Merge pull request #931 from mindlace-mp/writable-nested-modelserializer

Merged master into writable-nested-modelserializer.
Don't raise AttributeError on views with no model or queryset, when using DjangoModelPermissions
Merge remote-tracking branch 'upstream/writable-nested-modelserializer' into writable-nested-modelserializer
Merge remote-tracking branch 'upstream/master' into writable-nested-modelserializer