Updates build script

Author: mcsong

build.gradle

@@ -7,7 +7,7 @@ buildscript {
 
 	dependencies {
 		//classpath 'com.android.tools.build:gradle:1.1.2'
-		classpath 'com.android.tools.build:gradle:1.3.0'
+		classpath 'com.android.tools.build:gradle:2.1.2'
 		classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.1'
 		classpath 'com.github.dcendents:android-maven-plugin:1.2'
 		// NOTE: Do not place your application dependencies here; they belong