Update build tools and SDK version
Update build tools and SDK version

* Gradle build tools -> 1.3.1
* compileSdkVersion -> 23
* buildToolsVersion -> 23.0.1
* targetSdkVersion -> 23

braintree/braintree_android,braintree/braintree_android,braintree/braintree_android,braintree/braintree_android