The problem with API 23 and Google Play Services is still not resolved.

Just in case you get something like “unable to compute hash of /intermediates/classes-proguard/release/classes.jar” – just add a few lines to the proguard-rules.pro.

-dontwarn org.apache.http.**
-dontwarn android.net.http.AndroidHttpClient
-dontwarn com.google.android.gms.**
-dontwarn com.android.volley.toolbox.**

Stack overflow thread: http://stackoverflow.com/questions/30705589/gradle-build-failure
Star google bug: https://code.google.com/p/android-developer-preview/issues/detail?id=3001

//DL