Update views.py
Set base class for view mixin to MultipleObjectMixin
Make context name for a filter form configurable
Check filterform validity before calling filter()
Add docstrings to the view mixin
Fix django deprecation warning about deepcopy
Version update: 0.3.3
Merge /home/erwin/Temp/django-datafilters

Conflicts:
	datafilters/filterform.py
	datafilters/views.py