* Move auth backends into sso app.
* Add support for mapping social auth users into organizations and teams.
* Return social auth backends in a consistent order in the API.
* Remove custom SAML attribute mapping and use options provided by PSA.
* Add pipeline function to raise an exception if no user has been found or created; added comments on how to disable new user creation.
* Add comments for defining a custom social auth pipeline function.
* Fix an issue I created overriding authenticate
* Fix up attribute mapping using an identity provider class. The
methods built into django-social-auth for saml are probably not going
to work. We also now expose those mappings in a settings attrs map
that the user can override.
