Fix deprecation warnings and drop support for Django 1.11

[mscansian]

• Sets a default_auto_field Django 3.2
• Fix django.conf.urls deprecation warnings Django 2.0
• Drop support for Django 1.11

Dropping support for Django 1.11

The changes made to django.conf.urls are not compatible with Django 1.11. With the release of Django 4.0 (which will happen any time soon), django.conf.urls will be removed leaving users with a broken dependency (in case we don't fix it).

[tpazderka]

Thanks for your contribution!

I am fine with dropping 1.11.

@stinovlas what are your thoughts?

[stinovlas]

isort in quality check is failing. Other than that, I agree. LGTM

[mscansian]

isort in quality check is failing. Other than that, I agree. LGTM

Fixed

@stinovlas @tpazderka

[stinovlas]

@tpazderka LGTM. If you're OK with this as well, please merge the PR.

@mscansian Thanks for the contribution :-)!

[tpazderka]

Rebased and merged.

@mscansian Thanks for the contrbuition!

[mscansian]

@tpazderka Hey, is it possible to release the changes to PyPI?

[tpazderka]

We need to deal with #146 first as the master branch is currently broken for existing users.