Add djoser to authentication docs.
Add to main 3rd party resources list.
Merge pull request #1959 from konradhalas/add-djoser-to-docs

Add djoser to authentication docs
Set up serializer fields lazily on-demand.

This avoids AppRegistryNotReady problems in Django 1.7 with nested serializers,
which are instantiated at import time, possibly before Django's app registry is
fully populated.