Feature/slow binary handling

[gp-greg]

This PR adds an optimization for binary responses based on content type. This was originally documented as Issue 394 in the bravado repository.

[macisamuele]

@greenphire-greg thanks a lot for contributing.
NOTE: this is a quick first pass (did not check all the details)

Checking at the issue and at your PR I have a couple of suggestions

• bravado unmarshaling is performed here and not in bravado-core (probably the bravado-core is some dead code that we should eventually remove)
• I would suggest to avoid to mark all the possible mime types that reflect binary formats as this is not scalable.
  Maybe changing the "default" response type would be an option (even thought I'm not sure), an other option to overcome the scalability issue could be to add a configuration that lists all the mime types that need to return response.raw_bytes
• please install the hooks on your repository such that you can easily fix the travis failure (make install-hooks)

[coveralls]

Coverage increased (+0.009%) to 98.466% when pulling a987342 on Greenphire:feature/slow-binary-handling into 18e3574 on Yelp:master.

[gp-greg]

Alright, I'll close this and resubmit to the bravado repo.

[macisamuele]

@greenphire-greg thanks for the understanding and for helping us in making the tool better