Minor typo fix in models.py
Update models.py

Now using `django.contrib.auth.get_auth_user` instead of
`settings.AUTH_USER_MODEL` to get an actual model class instead of a
string. With this a bug is resolved when connecting
`email_address_handler` to the `User`'s `post_save`.
Remove one useless save call.
Adds django messages to `set_as_primary` view.
Merge pull request #5 from volrath/master

Minor typo fix in models.py