Added jsonp support
Determining transformable correctly for Collections
Minor adjustments and clarifying some tests for future reference.

Signed-off-by: Jason Lewis <jason.lewis1991@gmail.com>
Refactored : ResponseFormatInterface -> AbstractResponseFormat
  - All response formats should now have the request accessible
Force response status code to 200 OK when requesting jsonp else body may be dropped
404 should be implemented
- Don't monkey patch status codes for jsonp
- Use 400 instead of 422 for increased compatibility for clients.

See comments in https://github.com/dingo/api/pull/35 for rational.
Tweaking some JSONP things.

Signed-off-by: Jason Lewis <jason.lewis1991@gmail.com>
Merge branch 'feature/jsonp'