wip: mark areas that need to change for better response and error handling

[jzaefferer]

This isn't meant as a patch, more as a bug report or feature request. Tests fail, and should until its clear what really needs to change here.

The two issues I'd like to address:

• A 204 response with an empty body should be okay, and not lead to a rejection
• Handling response body in the error case needs be more flexible. In my case I'm expecting a single error property. I can imagine a callback for processing the error response, with the default handler implementing the current behaviour (looking for error.errors)

[masylum]

Will check it out ASAP. The behaviours you are changing make sense.

[jzaefferer]

After some improvements to my custom implementation, I've updated this to expose the response status code. Mostly to check for 401 errors and log out the user.