Update old dependencies

[sebastian-correa]

Closes #22 and #24.

Updating the dependencies brought some problems, that are fixed in 28b016e.

Problem 1

Trying to authenticate against the API errored out. I checked the django logs (/var/log/django/django.log) and there was an error with decoding and enconding the token.

jwt.encode returns a str since version 2.0, as seen in the changelog. The line

return token.decode('utf-8')

in models.py raised an AttributeError because token is a str.

Also, jwt.decode now needs an explicit declaration of the algorithm to use in order to work correctly.

Problem 2

The gunicorn config file had to be changed to a .py file.

Problem 3

app_name variable was added in django applications.

[kris621294]

5bcb07b4ecd61afd6dbeef5ed8975c086762bdde