Allow using third party SortedManyToManyField
(https://pypi.python.org/pypi/django-sortedm2m)
Merge branch 'master' of github.com:jdriscoll/django-photologue

Conflicts:
	photologue/models.py
Need to explicitly define USE_SORTEDM2M after import cleanup
Merge branch 'master' into sorted-m2m
Activate sortedm2m in example project.
Linting source code.
Migrating existing projects to use sortedm2m.
Update docs about sorted-m2m.
Tried to make sorted-m2m a conditional install, but this messes with South.

South wants to know the database schema at a given point in time, this won’t work if the field type depends on a setting.
Add django-sortedm2m to requirements.