update gradle to 2.2.0

build.gradle

@@ -5,7 +5,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.1.3'
+        classpath 'com.android.tools.build:gradle:2.2.0'
         classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
 
         // NOTE: Do not place your application dependencies here; they belong