Fixed issue of not having AUTH_USER_MODEL setting in Django 1.4
Fixed issue of not having AUTH_USER_MODEL setting in Django 1.4

If we can't find user model specified in settings - we go back to
previous/old way of grabbing user model (straight import)

MartinPetkov/django-security,issackelly/django-security,barseghyanartur/django-security,barseghyanartur/django-security,MartinPetkov/django-security,issackelly/django-security