Update managers.py

Fixes for Django 1.6 (as of beta 1)
Update managers.py

Editing comments.
Update managers.py

fixed bad indent.
Updating text to reflect macaddr regex tests for Django 1.6

macaddr searches were broken pre 1.6.  Updated test to reflect the correct way to regex search on a macaddr.
Merge pull request #17 from jmacul2/master

Fixes for Django 1.6