Merge branch 'custom-serializer-form-class' of https://github.com/ludwigkraatz/django-rest-framework into mergebranch#390

Conflicts:
	rest_framework/fields.py
	rest_framework/renderers.py
Manually solved

Update django-filter to released version.

Fix location of obtain_auth_token view

api-guide/views.md - add imports to code example

Tutorial: fix module name in section 3

Tutorial: fix module name in section 2

Again snippet -> snippets, but then it could be simpler (and possibly intended) to rename snippets to snippet in the first section of the tutorial.

snippet -> snippets (to match section 1).

* It wasn't clear where `Response` should be imported from.

Cache all fields per serializer instance

Add widgets for DateField and DateTimeField

Add support for partial serializer updates

http://www.python.org/dev/peps/pep-0008/#programming-recommendations

minor docs fix

http://www.python.org/dev/peps/pep-0008/#programming-recommendations

added RegexField

Conflicts:
	docs/topics/release-notes.md