Use tox for automating tests in different venvs

[tinvaan]

Is your feature request related to a problem? Please describe.
Tox project(https://tox.wiki) seems like a more useful addition to this project and can be used in place of Makefiles to invoke tests and other automations.

Tox also allows isolated builds against multiple virtual environments and is tailor-made for Python projects.

Describe the solution you'd like
We can drop the Makefiles in favour of tox.ini setup scripts. I have a sample PR opened at tinvaan#1

What do we feel about this?

[tinvaan]

/cc @J0, @olirice , @silentworks ^ bumping this, thanks.

[J0]

I’ll take a look at your PRs soon, thanks for the contributions!

[silentworks]

This would be a shift in the workflow of what everyone on the project is used to and introducing a new config to new developers on this project will be harder than a Makefile which they might have been introduced to before. Makefiles are more universal and in my opinion easier to read and understand. This Tox configuration file takes a while to understand, also the benefit of the isolated Python env is already available in our CI. I'm going to reject this change for now as it will cause more friction than anything else.