Update OmniAuth dependency to 0.3.0
Update to Code School v2 API & use Faraday parser

No need to use MultiJSON to parse the Faraday response object,
it comes with its own `parsed` method.

Calling the brand new Code School v2 API to retrieve `user_info`.
Remove naive first/last name splitting, add image.

Splitting the first and last word from the full name is terrible idea and
we should never ever do that.

Now including the user's avatar in the user_info hash because... you
know, that could be useful.