diff --git a/.gitignore b/.gitignore
index 79c8a51b..dca31695 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,5 @@ atlassian-ide-plugin.xml
 .idea/tasks.xml
 .idea/uiDesigner.xml
 .idea/libraries/
-build
\ No newline at end of file
+build
+local.properties
\ No newline at end of file
diff --git a/.idea/compiler.xml b/.idea/compiler.xml
index 9a8b7e5c..217af471 100644
--- a/.idea/compiler.xml
+++ b/.idea/compiler.xml
@@ -19,4 +19,5 @@
       </profile>
     </annotationProcessing>
   </component>
-</project>
\ No newline at end of file
+</project>
+
diff --git a/.idea/encodings.xml b/.idea/encodings.xml
index 13692363..e206d70d 100644
--- a/.idea/encodings.xml
+++ b/.idea/encodings.xml
@@ -1,7 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="Encoding" useUTFGuessing="true" native2AsciiForPropertiesFiles="false">
-    <file url="file://$PROJECT_DIR$" charset="UTF-8" />
-    <file url="file://$PROJECT_DIR$/android-app-tests/build.gradle" charset="UTF-8" />
-  </component>
-</project>
\ No newline at end of file
+  <component name="Encoding" useUTFGuessing="true" native2AsciiForPropertiesFiles="false" />
+</project>
+
diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 35db5fb0..0d7d4561 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -18,4 +18,5 @@
       </GradleProjectSettings>
     </option>
   </component>
-</project>
\ No newline at end of file
+</project>
+
diff --git a/.idea/misc.xml b/.idea/misc.xml
index 41c22422..92954b82 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,42 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="CompilerConfiguration">
-    <option name="DEFAULT_COMPILER" />
-    <resourceExtensions />
-    <wildcardResourcePatterns>
-      <entry name="!?*.java" />
-      <entry name="!?*.form" />
-      <entry name="!?*.class" />
-      <entry name="!?*.groovy" />
-      <entry name="!?*.scala" />
-      <entry name="!?*.flex" />
-      <entry name="!?*.kt" />
-      <entry name="!?*.clj" />
-    </wildcardResourcePatterns>
-    <annotationProcessing>
-      <profile default="true" name="Default" enabled="false">
-        <processorPath useClasspath="true" />
-      </profile>
-    </annotationProcessing>
-  </component>
-  <component name="CopyrightManager" default="" />
   <component name="DaemonCodeAnalyzer">
     <disable_hints />
   </component>
-  <component name="DependencyValidationManager">
-    <option name="SKIP_IMPORT_STATEMENTS" value="false" />
-  </component>
-  <component name="Encoding" useUTFGuessing="true" native2AsciiForPropertiesFiles="false" />
   <component name="EntryPointsManager">
     <entry_points version="2.0" />
   </component>
-  <component name="GradleLocalSettings">
-    <option name="modificationStamps">
-      <map>
-        <entry key="$PROJECT_DIR$" value="9952879223627" />
-      </map>
-    </option>
-  </component>
   <component name="NullableNotNullManager">
     <option name="myDefaultNullable" value="javax.annotation.Nullable" />
     <option name="myDefaultNotNull" value="javax.annotation.Nonnull" />
@@ -71,20 +40,9 @@
     <ConfirmationsSetting value="0" id="Add" />
     <ConfirmationsSetting value="0" id="Remove" />
   </component>
-  <component name="ProjectModuleManager">
-    <modules />
-  </component>
   <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" assert-keyword="true" jdk-15="true" project-jdk-name="1.7" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
-  <component name="PropertiesComponent">
-    <property name="GoToClass.includeLibraries" value="false" />
-    <property name="GoToClass.toSaveIncludeLibraries" value="false" />
-    <property name="GoToFile.includeJavaFiles" value="false" />
-    <property name="MemberChooser.sorted" value="false" />
-    <property name="MemberChooser.showClasses" value="true" />
-    <property name="MemberChooser.copyJavadoc" value="false" />
-  </component>
   <component name="RunManager">
     <configuration default="true" type="#org.jetbrains.idea.devkit.run.PluginConfigurationType" factoryName="Plugin">
       <module name="" />
@@ -199,4 +157,5 @@
       </state>
     </states>
   </component>
-</project>
\ No newline at end of file
+</project>
+
diff --git a/.idea/modules.xml b/.idea/modules.xml
index b44e84c8..99134cac 100644
--- a/.idea/modules.xml
+++ b/.idea/modules.xml
@@ -8,4 +8,5 @@
       <module fileurl="file://$PROJECT_DIR$/core/core.iml" filepath="$PROJECT_DIR$/core/core.iml" />
     </modules>
   </component>
-</project>
\ No newline at end of file
+</project>
+
diff --git a/.idea/runConfigurations/Debug.xml b/.idea/runConfigurations/Debug.xml
deleted file mode 100644
index 4e3c720a..00000000
--- a/.idea/runConfigurations/Debug.xml
+++ /dev/null
@@ -1,26 +0,0 @@
-<component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="Debug" type="AndroidRunConfigurationType" factoryName="Android Application">
-    <module name="android-app" />
-    <option name="ACTIVITY_CLASS" value="" />
-    <option name="MODE" value="do_nothing" />
-    <option name="DEPLOY" value="false" />
-    <option name="ARTIFACT_NAME" value="" />
-    <option name="TARGET_SELECTION_MODE" value="SHOW_DIALOG" />
-    <option name="USE_LAST_SELECTED_DEVICE" value="true" />
-    <option name="PREFERRED_AVD" value="" />
-    <option name="USE_COMMAND_LINE" value="true" />
-    <option name="COMMAND_LINE" value="" />
-    <option name="WIPE_USER_DATA" value="false" />
-    <option name="DISABLE_BOOT_ANIMATION" value="false" />
-    <option name="NETWORK_SPEED" value="full" />
-    <option name="NETWORK_LATENCY" value="none" />
-    <option name="CLEAR_LOGCAT" value="false" />
-    <option name="SHOW_LOGCAT_AUTOMATICALLY" value="true" />
-    <option name="FILTER_LOGCAT_AUTOMATICALLY" value="true" />
-    <RunnerSettings RunnerId="AndroidDebugRunner" />
-    <ConfigurationWrapper RunnerId="AndroidDebugRunner" />
-    <method>
-      <option name="Make" enabled="false" />
-    </method>
-  </configuration>
-</component>
\ No newline at end of file
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
index 83067447..276779e8 100644
--- a/.idea/vcs.xml
+++ b/.idea/vcs.xml
@@ -4,4 +4,5 @@
     <mapping directory="" vcs="Git" />
     <mapping directory="$PROJECT_DIR$" vcs="Git" />
   </component>
-</project>
\ No newline at end of file
+</project>
+
diff --git a/android-app-tests/android-app-tests.iml b/android-app-tests/android-app-tests.iml
index ad249d00..06d823d7 100644
--- a/android-app-tests/android-app-tests.iml
+++ b/android-app-tests/android-app-tests.iml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<module external.linked.project.id=":android-app-tests" external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$/.." external.system.id="GRADLE" external.system.module.group="calculatorpp" external.system.module.version="unspecified" type="JAVA_MODULE" version="4">
+<module external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$/.." external.system.id="GRADLE" external.system.module.group="calculatorpp" external.system.module.version="unspecified" type="JAVA_MODULE" version="4">
   <component name="FacetManager">
     <facet type="android-gradle" name="Android-Gradle">
       <configuration>
@@ -31,6 +31,8 @@
     <orderEntry type="library" exported="" scope="TEST" name="robolectric-2.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="mockito-all-1.9.5" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="jsonassert-1.2.3" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="support-v4-21.0.3" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="appcompat-v7-21.0.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="hamcrest-core-1.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="objenesis-1.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="sqlite4java-0.282" level="project" />
@@ -42,7 +44,6 @@
     <orderEntry type="library" exported="" scope="TEST" name="commons-codec-1.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="httpclient-4.0.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="vtd-xml-2.11" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="support-v4-19.0.1" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="fest-util-1.2.5" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="fest-reflect-1.4.1" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="maven-ant-tasks-2.1.3" level="project" />
@@ -71,38 +72,40 @@
     <orderEntry type="library" exported="" scope="TEST" name="wagon-http-shared-1.0-beta-6" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="xercesMinimal-1.9.6.2" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="nekohtml-1.9.6.2" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="support-annotations-21.0.3" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="simple-xml-2.6.1" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="core" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="commons-cli-1.2" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="annotations-2.0.1" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="core" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="internal_impl-21.0.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="stax-1.2.0" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="jscl-1.0.9" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="support-annotations-21.0.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="common-msg-1.0.5" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="common-listeners-1.0.7" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="guava-11.0.2" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="common-text-1.0.7" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="library-2.4.0" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="common-text-1.0.7" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="acra-4.5.0" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="common-core-1.0.7" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="_home_serso_projects_java_android_calculatorpp_android_app_build_intermediates_exploded_aar_org_solovyev_android_material_0_1_2_classes_jar" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="jscl-1.0.8" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="internal_impl-21.0.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="common-core-1.0.7" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="common-security-1.0.7" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="_home_serso_projects_java_android_calculatorpp_android_app_build_intermediates_exploded_aar_org_solovyev_android_checkout_0_6_1_classes_jar" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="classes" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="_home_serso_projects_java_android_calculatorpp_android_app_build_intermediates_classes_debug" level="project" />
-    <orderEntry type="library" exported="" scope="TEST" name="_home_serso_projects_java_android_calculatorpp_android_app_build_intermediates_dependency_cache_debug" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="_home_serso_projects_java_serso_android_calculatorpp_android_app_build_intermediates_classes_debug" level="project" />
+    <orderEntry type="library" exported="" scope="TEST" name="_home_serso_projects_java_serso_android_calculatorpp_android_app_build_intermediates_dependency_cache_debug" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="android" level="project" />
   </component>
-</module>
\ No newline at end of file
+</module>
+
diff --git a/android-app/android-app.iml b/android-app/android-app.iml
index 1e7c9b97..f21746b2 100644
--- a/android-app/android-app.iml
+++ b/android-app/android-app.iml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<module external.linked.project.id=":android-app" external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$/.." external.system.id="GRADLE" external.system.module.group="org.solovyev.android" external.system.module.version="2.1.0" type="JAVA_MODULE" version="4">
+<module external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$/.." external.system.id="GRADLE" external.system.module.group="org.solovyev.android" external.system.module.version="2.1.0" type="JAVA_MODULE" version="4">
   <component name="FacetManager">
     <facet type="android-gradle" name="Android-Gradle">
       <configuration>
@@ -9,6 +9,7 @@
     <facet type="android" name="Android">
       <configuration>
         <option name="SELECTED_BUILD_VARIANT" value="debug" />
+        <option name="SELECTED_TEST_ARTIFACT" value="_android_test_" />
         <option name="ASSEMBLE_TASK_NAME" value="assembleDebug" />
         <option name="COMPILE_JAVA_TASK_NAME" value="compileDebugSources" />
         <option name="ASSEMBLE_TEST_TASK_NAME" value="assembleDebugTest" />
@@ -24,6 +25,7 @@
   </component>
   <component name="NewModuleRootManager" inherit-compiler-output="false">
     <output url="file://$MODULE_DIR$/build/intermediates/classes/debug" />
+    <output-test url="file://$MODULE_DIR$/build/intermediates/classes/test/debug" />
     <exclude-output />
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/build/generated/source/r/debug" isTestSource="false" generated="true" />
@@ -114,4 +116,5 @@
     <orderEntry type="library" exported="" name="simple-xml-2.6.1" level="project" />
     <orderEntry type="module" module-name="core" exported="" />
   </component>
-</module>
\ No newline at end of file
+</module>
+
diff --git a/calculatorpp.iml b/calculatorpp.iml
index 3edd6408..0bb6048a 100644
--- a/calculatorpp.iml
+++ b/calculatorpp.iml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<module external.linked.project.id="calculatorpp" external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$" external.system.id="GRADLE" external.system.module.group="" external.system.module.version="unspecified" type="JAVA_MODULE" version="4">
+<module external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$" external.system.id="GRADLE" external.system.module.group="" external.system.module.version="unspecified" type="JAVA_MODULE" version="4">
   <component name="FacetManager">
     <facet type="java-gradle" name="Java-Gradle">
       <configuration>
@@ -15,4 +15,5 @@
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
   </component>
-</module>
\ No newline at end of file
+</module>
+
diff --git a/core/core.iml b/core/core.iml
index 22ed83ea..89e82795 100644
--- a/core/core.iml
+++ b/core/core.iml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<module external.linked.project.id=":core" external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$/.." external.system.id="GRADLE" external.system.module.group="calculatorpp" external.system.module.version="unspecified" type="JAVA_MODULE" version="4">
+<module external.linked.project.path="$MODULE_DIR$" external.root.project.path="$MODULE_DIR$/.." external.system.id="GRADLE" external.system.module.group="calculatorpp" external.system.module.version="unspecified" type="JAVA_MODULE" version="4">
   <component name="FacetManager">
     <facet type="android-gradle" name="Android-Gradle">
       <configuration>
@@ -42,4 +42,5 @@
     <orderEntry type="library" exported="" scope="TEST" name="hamcrest-core-1.3" level="project" />
     <orderEntry type="library" exported="" scope="TEST" name="objenesis-1.0" level="project" />
   </component>
-</module>
\ No newline at end of file
+</module>
+