Allow nested fields to be missing

Adds BLANK_CHOICE_DASH as a choice item

Conflicts:
	rest_framework/tests/fields.py

Updated the dependencies version and added the ALLOWED_HOSTS for tests.

fix function names and dotted lookups for use in PrimaryKeyRelatedField

add tests for dotted lookup in RelatedField, PrimaryKeyRelatedField, and HyperlinkedRelatedField. #694

Forms in Broseable API support dynamic serializers based on request method

Fix typo + grammar in viewsets docs

HyperlinkedIdentityField uses `lookup_field` kwarg.

According to the [Serializers API Guide][1], `HyperlinkedIdentityField`
takes `lookup_field` as a kwarg like the other related fields and the
generic views. However, this was not actually implemented.

[1]: http://django-rest-framework.org/api-guide/serializers.html#hyperlinkedmodelserializer

Small typo in the ViewSet example.

Remove trailing unmatched </div> in login_base.html template. Reformat i...