Tests for DjangoModelPermissions.
Bugfix for DjangoModelPermissions.  Fixes #437

Turns out that Django's default permissions backend always returns
False when checking object-level permissions, even if the user does
have valid global permissions.
Improve relations documentation.
Change URL of 2.2 announcement
Enforce PUT-as-create permissions
Fix incorrect 401 vs 403 response, if lazy authentication has not taken place.
Add object permissions tests.
Make use o issubclass instead of isinstance (fix issue #645)

Because __mro__ is a list of classes and not instances.
DictWithMetadata.__getstate__ was never called

Signed-off-by: Fernando Rocha <fernandogrd@gmail.com>
Merge pull request #651 from fernandogrd/master

DictWithMetadata.__getstate__ was never called (Fix for 645)
New style object-level permission checks
Tidy up internal view permission checking logic.

Also document correctly - these methods are now public and will fall
under the deprecation policy from now on.
Use `many=True` for serializers.
Notes on object-level permissions.
Drop `six` module from coverage.
Notes on object-level permissions.
Update release notes
Document serializing querysets
Raise warnings on implicit many serialization
Raise warnings if 'request' not in context for hyperlinked fields.
Docs on serializer context.