tipfy.ext.auth.providers.facebook was ported from
`tornado.auth <http://github.com/facebook/tornado/blob/master/tornado/auth.py>`_.

Tornado is licensed under the Apache Licence, Version 2.0
(http://www.apache.org/licenses/LICENSE-2.0.html).

Copyright (c) 2009 Facebook.
Copyright (c) 2010 tipfy.org.
