add gson

Signed-off-by: tobiaskaminsky <tobias@kaminsky.me>

build.gradle

@@ -228,6 +228,8 @@ dependencies {
     implementation 'com.caverock:androidsvg:1.2.1'
     implementation "com.android.support:support-annotations:${supportLibraryVersion}"
 
+    compile 'com.google.code.gson:gson:2.8.2'
+
     // dependencies for local unit tests
     testImplementation 'junit:junit:4.12'
     testImplementation 'org.mockito:mockito-core:1.10.19'