Adds `get_query_set` fallback
Adds `get_query_set` fallback

as per docs https://docs.djangoproject.com/en/1.7/releases/1.6/#get-query-set-and-similar-methods-renamed-to-get-queryset

coleifer/django-generic-m2m,coleifer/django-generic-m2m,coleifer/django-generic-m2m