The branches as of current, master and A.S.-2.1, are used for separate versions for Android Studio. Master is in line with v3.0 + android studio with the usage of implementation instead of compile. The branch A.S.-2.1 is inline with versions before v3.0 and specifically v2.1 utilizing compile instead of implementation.

NOTICE

IF YOU ARE HAVING ISSUES COMPILING GRADLE CHECK YOUR ANDROID STUDIO VERSION!