[deps] Add support for latest django-rest-framework-version

[nemesifier]

Add support for latest django-rest-framework-version (tox, ensure tests pass, update compatibility table).

[Akshat1Nar]

Hello, I will like to take this, Can you guide me a little bit @nemesisdesign .

[dhaval-mehta]

#223 is running the test against DRF 3.12 and tests are passing after a few minor fixes.

[nemesifier]

Closed by #223, thanks @dhaval-mehta 👍

[nemesifier]

Just realized that the CI build doesn't seem to test with the latest version of DRF, let's fix this!

[devkapilbansal]

Done in #266