In Django < 1.7, if settings.AUTH_USER_MODEL is defined, the sender is expected to be the actual instance, not a string. This Closes rossp/django-helpdesk#295 by checking for django version < 1.7.
In Django < 1.7, if settings.AUTH_USER_MODEL is defined, the sender is expected to be the actual instance, not a string. This Closes rossp/django-helpdesk#295 by checking for django version < 1.7.

gwasser/django-helpdesk,django-helpdesk/django-helpdesk,gwasser/django-helpdesk,harrisonfeng/django-helpdesk,fjcapdevila/django-helpdesk,rossp/django-helpdesk,temnoregg/django-helpdesk,mrkiwi-nz/django-helpdesk,django-helpdesk/django-helpdesk,mrkiwi-nz/django-helpdesk,rossp/django-helpdesk,django-helpdesk/django-helpdesk,fjcapdevila/django-helpdesk,gwasser/django-helpdesk,mrkiwi-nz/django-helpdesk,django-helpdesk/django-helpdesk,rossp/django-helpdesk,chriscauley/django-helpdesk,mrkiwi-nz/django-helpdesk,harrisonfeng/django-helpdesk,chriscauley/django-helpdesk,harrisonfeng/django-helpdesk,chriscauley/django-helpdesk,chriscauley/django-helpdesk,gwasser/django-helpdesk,fjcapdevila/django-helpdesk,temnoregg/django-helpdesk,fjcapdevila/django-helpdesk,rossp/django-helpdesk,temnoregg/django-helpdesk,harrisonfeng/django-helpdesk,temnoregg/django-helpdesk