volley android client does not compile because of Responses.BooleanResponse

It seems there is an interface that is not generated in `Responses`:

``` java
public void isRunning (final Responses.BooleanResponse responseListener,
  final Response.ErrorListener errorListener) {}
```

This code is generated into one of the API classes, yet `Responses.BooleanResponse` does not exist. I think it is missing from the generator.
