Prevent DeprecationWarnings from being raised while running API tests.

* Explicitly pass `many=True` when instantiating a serializer with an iterable.
* Add `request` to the context of subclasses of hyperlinked fields when directly testing the fields' classes.
* Instantiate serializers containing hyperlinked fields with contexts containing `request` when directly testing the serializers' classes.
Merge pull request #1529 from chuckharmston/deprecation_warnings_gone

Prevent DeprecationWarnings from being raised while running API tests.