Adds gson to test deps and extracts version variable

Author: Josh Deffibaugh

android-sdk/build.gradle

@@ -48,6 +48,7 @@ dependencies {
     androidTestCompile "com.google.dexmaker:dexmaker:$dexmaker_ver"
     androidTestCompile "com.google.dexmaker:dexmaker-mockito:$dexmaker_ver"
     androidTestCompile "com.noveogroup.android:android-logger:$android_logger_ver"
+    androidTestCompile "com.google.code.gson:gson:$gson_ver"
 }
 
 uploadArchives {

build.gradle

@@ -35,6 +35,7 @@ ext {
     support_test_runner_ver = "0.5"
     dexmaker_ver = "1.2"
     espresso_ver = "2.2.2"
+    gson_ver = "2.6.2"
     version_name = "0.0.1"
     group_id = "com.optimizely.ab"
 }

test-app/build.gradle

@@ -30,7 +30,7 @@ dependencies {
     // Includes SST Java core, event handler, and user experiment record
     compile project(':android-sdk')
 //    compile 'com.optimizely.ab:android-sdk:0.0.1'
-    compile 'com.google.code.gson:gson:2.6.2'
+    compile "com.google.code.gson:gson:$gson_ver"
     compile 'com.android.support:appcompat-v7:24.2.1'
     compile 'com.android.support:design:24.2.1'