Added missing default style for FileField
Improved nested update test in update().

Closes #2194.
Improve nested update and create testing.
Renamed validated_attrs to validated_data to be more in line with other similar code.
Merge pull request #2196 from tomchristie/tomchristie-improve-update-nested-validation

Improve checks for nested creates and updates.
Merge pull request #2197 from mtschammer/mtschammer-validated_attrs-rename

Renamed validated_attrs to validated_data to be more in line with other code
Merge pull request #2172 from kchange/master

Added missing default style for FileField
Merge branch 'master' of github.com:tomchristie/django-rest-framework