Add msgpack support

[AlstonLin]

msgpack would be a more efficient way to receive large JSON body responses, and could mean large performance gains for people who want to use bravado with a server that supports application/msgpack responses

Support for this content type should be added to bravado

[AlstonLin]

@macisamuele For this functionality, one of the things I'd need to do is to add msgpack unmarshalling in bravado_core. However, to be able to do that I need to have access to the bytes of a response, which is currently not possible under the interface specified in bravado_core.response.IncomingResponse. So to implement this, I'd need to change IncomingResponse to have 'bytes' in the required_attrs, which would be a breaking change as now all implementations of this, including the RequestsResponseAdapter and FidoResponseAdapter in bravado will need to be updated to use the latest version of bravado_core if pushed. This means that this feature would require a breaking change to bravado_core. Would you say this is a feature worth having a breaking change?

[macisamuele]

@AlstonLin this is just to recap our quick chat 😄
We can modify IncomingResponse in order to expose bytes other than text and json, it should not be a breaking change but according to how it will be implemented, we can decide whenever is safe to go with a minor version bump or a major version bump.

I checked bravado-core and bravado implementations and those are the points that I would focus (it doesn't represent a limitation to you, it's more about giving ahead places to look in order to overcome the 9 hours gap):

• modify bravado_core.response.IncomingResponse and bravado_core.response.OutgoingResponse in order to expose bytes
• define a constant (like APP_JSON) for handling msgpack content, update bravado_core.response.unmarshal_response
• we should update bravado.request_client.RequestResponseAdapter, bravado.fido_client.FidoResponseAdapter and set minimum bravado-core dependency on bravado setup.py
• we should update pyramid_swagger.tween.PyramidSwaggerRequest and pyramid_swagger.tween. PyramidSwaggerResponse in order to expose bytes and set minimum bravado-core dependency on pyramid-swagger

I'm pretty sure that I'm still missing something, but surely you'll figure it out 😄