Djangorestframework-simplejwt

* Restricted `setup.py` config to Python 3 only.

* Included translation files in release package.

* Updated `python-jose` version requirement.

* Fixed `KeyError` in `TokenObtainSerializer.validate`.

* Added request pass-through on `django.contrib.auth.authenticate` call in
`TokenObtainSerializer`.
* Updated `TokenObtainSerializer` to use `fail` API from parent class.

* Added language support for Brazilian Portuguese.
* Added support for automatic username lookup in `TokenUser`.