Fixed status code errors by calling _process_options

Needed to use the `_process_options` method explicitly because the overriding of `render_to_body` in the `ControllerAdditions` module removes it from the call chain.

Should resolve https://github.com/apotonick/roar-rails/issues/71
I like your approach way better :heart:  Overriding `#render_to_body` was more like a work-around that made its way into public :/

For a better understanding, where is that `_render_option_json` called?