Add Django 2.2, 3.0(a) to tests, dropped Django 2.0, py3.4

[therefromhere]

Resolves #196

[therefromhere]

I'm not sure why some of the tests are failing on travis, tox is passing for me locally.

It seems to be something specific to Django>=2.2, maybe something subtly wrong with the settings setup in runtests.py? I'd be tempted to remove nose/runtests.py and see if it goes away with pytest-django and a more normal settings file in tests/settings.py.

[therefromhere]

(for what it's worth I'm using django-extra-views with Django 2.2 in prod with no issues).

[jonashaag]

If we can easily get rid of nose I'm all for it.

[therefromhere]

I think it's because of this from django.contrib.contenttypes.models import ContentType in extra_views_tests/models.py.

Also there are no migrations for the extra_views_tests models.

[codecov-io]

Codecov Report

Merging #197 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #197   +/-   ##
=======================================
  Coverage   83.93%   83.93%           
=======================================
  Files           4        4           
  Lines         386      386           
  Branches       48       48           
=======================================
  Hits          324      324           
  Misses         48       48           
  Partials       14       14

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[therefromhere]

I've fixed the tests, the failure was because extra_views_tests has models but didn't have migrations. No idea why it was passing locally and failing on travis though. Should be all good now.

[jonashaag]

Boy these codecov comments are annoying

[jonashaag]

Thanks!