Update django and python versions

[wittfabian]

A lot of the tested versions are deprecated.

[amitu]

Hey @wittfabian, thanks for alerting us. I have updated some versions. Can you please let me know what else needs updating?

[wittfabian]

I would remove the old versions (Python < 3 and Django < 1.11) Additionally add new versions (Python 3.7 and 3.8, Django 2. and 3.X)

[wittfabian]

Django 2.0 removes the django.core.urlresolvers module, which was moved to django.urls in version 1.10. You should change any import to use django.urls instead, like this:

from django.urls import reverse

See: https://github.com/wittfabian/django-encrypted-id