Draft: Refactor ci tests

[marteinn]

In this PR I have updated both the tox config, the travis CI config and github actions, I have done the following:

• Dropped Django 1 support
• Only used supported Wagtail versions (2.7 and 2.10)
• Only used supported Django versions (3.1, 3.0 and 2.2)

We should probably drop Travis in favor of github actions, I have chosen not to do this in this PR without discussion.

I'm also looking at optimizing the CI bit, its a lot of repetition taken place right now, we should be able to go from explicit to setting an array with ignore-rules.

[mvantellingen]

continued in #35

[marteinn]

@mvantellingen 👍