Updated build tools version to 19.1.0

build failed with Android Studio 0.6.0.

```
Error:The SDK Build Tools revision (19.0.1) is too low. Minimum required is 19.1.0
```

I've fixed this incompatible issue with below modification.

- Update Build Tools version.
Is this change required for Android Studio 0.6?
If yes, please use 'com.android.tools.build:gradle:0.10.+' instead, so that to maintain backward compatible.