update example

example/android/app/build.gradle

 
 android {
     compileSdkVersion 23
-    buildToolsVersion "23.0.3"
+    buildToolsVersion "25.0.1"
 
     defaultConfig {
         applicationId "com.example"

example/android/build.gradle

         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.2.0'
+        classpath 'com.android.tools.build:gradle:2.2.2'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files