Pin Django docs version for 1.4-style user profiles

Given that we're using 1.4's user profile rather than 1.5's custom User model we'll want the correct docs referenced.

As an alternative we could direct users to the updated docs (indicating deprecation of the ``AUTH_PROFILE_MODULE``: https://docs.djangoproject.com/en/dev/topics/auth/customizing/#extending-the-existing-user-model