Revert "Use gradle 1.2 instead of 2.1"

This reverts commit c1dfadd85b95417b3a07a99ff1bef5f265820e07.
Revert "Updated to android sdk 23.0.5"

This reverts commit 1670cc7e1d55228b56f1f3e5d9f9f3c9aaff31d3.
Release version mychat-1.0 with gradle 1.12, android-20, build-tools-20.0.0