User authentication via Twitter and Facebook and internal auth token

For Facebook auth/user creation, hit `/auth/facebook/token` with `access_token` parameter. For Twitter, hit `/auth/twitter/token` with `oauth_token`, `oauth_token_secret` and `user_id`.

The middleware checks for a `token` parameter in params/body/query respectively and sets the matching User to req.user if found.
OK to have a `secret` in a public repo?