update models.py imports for new application loading system
update models.py imports for new application loading system

treyhunner/django-simple-history,luzfcb/django-simple-history,emergence/django-simple-history,pombredanne/django-simple-history,emergence/django-simple-history,luzfcb/django-simple-history,treyhunner/django-simple-history,pombredanne/django-simple-history