User.create_with_omniauth  now supports google, facebook and twitter authentication.
Drop "friendly" user urls by github nickname since we are going to have multiple providers.
Controllers ready to support multiple authentication providers.
And UI is ready for logging in/signing up with twitter, google and facebook.
Merge branch '1-more_social_logins'. Closes https://github.com/euruko2013/vestibule/issues/1.