Update to android gradle plugin 2.1.2.

Changelog: https://developer.android.com/studio/releases/gradle-plugin.html#revisions

Author: plastiv

build.gradle

@@ -5,7 +5,7 @@ buildscript {
   }
 
   dependencies {
-    classpath 'com.android.tools.build:gradle:1.5.0'
+    classpath 'com.android.tools.build:gradle:2.1.2'
   }
 }