Fixes #639.

2.2 Release

Need to track outcome of Django's #19733, and decide on approach
accordingly.

Mostly adding `from __future__ import unicode_literals` everywhere.

Conflicts:
	rest_framework/relations.py
	rest_framework/serializers.py
	rest_framework/tests/relations_hyperlink.py
	rest_framework/tests/relations_slug.py

(instead of request.GET)

Commiter number 100!

Conflicts:
	rest_framework/authentication.py
	rest_framework/relations.py
	rest_framework/serializers.py
	rest_framework/settings.py
	rest_framework/tests/authentication.py
	rest_framework/tests/genericrelations.py
	rest_framework/tests/generics.py
	rest_framework/tests/relations_hyperlink.py
	rest_framework/tests/relations_nested.py
	rest_framework/tests/relations_pk.py
	rest_framework/tests/serializer.py

Conflicts:
	rest_framework/relations.py

Fix processing of ManyToManyField when it is empty 

Signed-off-by: Fernando Rocha <fernandogrd@gmail.com>

Signed-off-by: Fernando Rocha <fernandogrd@gmail.com>

For ensuring `django-jsonfield` compatibility, via #629.

Update rest_framework/serializers.py

Ensure model field validation is performed for ModelSerializers with a custom restore_object method.  Fixes #623.

Login page styles fix. Closes #618. Made with 🍪