@rustybox, I'm not a maintainer but I have some comments on this commit that I think might make it more likely to be merged in. If you like, I can make the changes and submit a separate pull request, as I'll probably make them anyway for my own use.

1. To avoid breaking existing client code, it might be better to add this as another overload rather than changing the signature. e.g.

        public void onSuccess(int statusCode, String content) {
            onSuccess(content);
        }
        public void onSuccess(int statusCode, Header[] headers, String content) {
            onSuccess(statusCode, content);
        }

2. The docstring should also be updated with the new parameter.
3. The changed formatting in the parameter list is inconsistent with the rest of the library.

Same things with the `JsonHttpResponseHandler`.