Additional suppressions for classes

[konradwojda]

Added two additional suppressions:

1. Suppress useless-super-delegation when docstrings are different in functions as it can be used in generating documentation for example in Swagger.

class NewView(ViewSet):
    def list(self):
        """Documentation"""
         return super().list()

2. Suppress abstract-method when inheriting from rest_framework.serializers.Serializer. According to documentation overriding create and update methods is optional.

[coveralls]

Coverage: 0.0%. Remained the same when pulling 07165f8 on konradwojda:additional-suppressions into b8217c1 on PyCQA:master.