Update model tests to include our new InheritanceManagerTestChild3 as part of the emulation of select_subclasses.
Update model tests to include our new InheritanceManagerTestChild3
as part of the emulation of select_subclasses.

Test still fails because of #59.

carljm/django-model-utils,timmygee/django-model-utils,nemesisdesign/django-model-utils,patrys/django-model-utils,carljm/django-model-utils,nemesisdesign/django-model-utils,yeago/django-model-utils,timmygee/django-model-utils,yeago/django-model-utils,patrys/django-model-utils