Updated :android manifest and build script

Added google() to repositories
Added game flags to manifest

android/AndroidManifest.xml

@@ -13,6 +13,8 @@
     <application
         android:allowBackup="true"
         android:icon="@drawable/ic_launcher"
+        android:isGame="true"
+        android:appCategory="game"
         android:label="@string/app_name"
         android:theme="@style/GdxTheme" >
         <activity

android/build.gradle

@@ -60,6 +60,7 @@ dependencies {
 }
 
 repositories {
+  google()
   jcenter()
 }