Django REST Framework getting start guide is out of date

[kevin-brown]

https://github.com/evonove/django-oauth-toolkit/blob/master/docs/rest-framework/getting_started.rst

There are a few issues in the getting started guide that make it difficult for users with upgraded versions of Django and Django REST Framework to use it.

• View.model property was deprecated in 2.4
• patterns is deprecated and on its way out