added geo support for PassThroughManager
edited class names
edited class names
edited doc string
removed GeoDjango specific code. Abstracted all managers
moved get_query_set = get_queryset from the mixin to the manager
Update managers.py
changed class names to be more descriptive
removed trailing whitespace
edited class names
added documentation about manager mixins
updated manager docs
edited typo
Minor docs cleanup.
Add changelog note.
Remove trailing whitespace.