Vimeo sends additional information in auth response

[karlvr]

Refer https://developer.vimeo.com/api/authentication

It's the final request with grant_type = authorization_code, in which Vimeo includes a "user" object to provide some information about who you've authed as. I'm not sure whether this is common practice. It would be pretty straight forward to add more parameters to the success block - but obviously this would be a breaking change. I wonder if other implementations might return information useful to the application in response headers; so maybe we need to pass the operation itself and the responseObject just to be future proof.

I'm going to experiment with this approach in a fork, so I'll be happy to submit a pull request. What do you think about this issue and possible approaches?