Fix bug with child/grandchild select_subclasses in Django 1.6+; thanks Keryn Knight.
Fixed indexing into Choices so its useful.
Merge branch 'master' into feature/model_subclasses

# By Carl Meyer
* master:
  Fixed indexing into Choices so its useful.
  Fix bug with child/grandchild select_subclasses in Django 1.6+; thanks Keryn Knight.

Conflicts:
	model_utils/tests/models.py