Add Testing Utils

[sarahcodes100]

As mentioned (https://github.com/mapzen/android/pull/260), it requires a LOT of setup to properly test calls to LocationServices.FusedLocationApi

Lets provide a way to do this for developers:

    FusedLocationProviderService.FusedLocationProviderBinder stubBinder =
          mock(FusedLocationProviderService.FusedLocationProviderBinder.class);
    FusedLocationProviderService mockService = mock(FusedLocationProviderService.class);
      when(stubBinder.getService()).thenReturn(mockService);
    FusedLocationProviderApiImpl impl =
        (FusedLocationProviderApiImpl) LocationServices.FusedLocationApi;
    impl.onServiceConnected(stubBinder);

Initial implementation ideas:

• Expose the FusedLocationProvider service with @VisibleForTesting annotation
• Create a separate artifact that adds classes to wrap these calls