Don't call standard login hooks

Since users are "audited" they require a call to "save_with_user". The
default hook here attempts to do something like:

user.last_login = today()
user.save()

Which causes an exception

This fix isn't really permanent, but it does enable login with the
django admin. In the future, we'll have to figure out how to handle this.
Disable the admin interface in production
Merge pull request #40 from ahinz/topic/fix-admin

Topic/fix admin