Django-useraudit

Resets Users that are blocked by django-useraudit and then re-activated by an admin to better defaults. More details in:

https://github.com/muccg/django-useraudit/issues/4

Also add a new signal `useraudit.signals.login_failure_limit_reached` that is sent when a user is deactivated. All signals have been moved to `useraudit.signals`:

https://github.com/muccg/django-useraudit/issues/6

Extension to `useraudit.backend.AuthFailedLoggerBackend` that allows to set login attempts limit.

Fixes an import problem that affects only Python 3.