Django 1.6 compatibility
Bugfix: Cannot unassign presentation on schedule/edit view
Merge branch 'django1.6-compatibility' of https://github.com/mbrochh/symposion into mbrochh-django1.6-compatibility

Conflicts:
	symposion/boxes/urls.py
	symposion/cms/urls.py
	symposion/conference/urls.py
	symposion/proposals/models.py
	symposion/proposals/urls.py
	symposion/reviews/urls.py
	symposion/schedule/models.py
	symposion/schedule/urls.py
	symposion/speakers/urls.py
	symposion/sponsorship/urls.py
	symposion/teams/urls.py
Merge branch 'mbrochh-django1.6-compatibility'