Included key with get_serializer_class

[snewcomer]

get_serializer_class method on the view doesn't work when trying to get included resources. Is this a pull request you would be open to (w/ tests of course!)?

[snewcomer]

This line seems to be the source of the err.

django-rest-framework-json-api/rest_framework_json_api/serializers.py

Line 97 in 4488068

this_serializer_class = view.serializer_class

[jerel]

@snewcomer from what I see that seems it should be replaced with a call to get_serializer_class. I would welcome a PR with test coverage

[jerel]

Closed by #213