WIP: contributing updates

[jessicaaustin]

Updates to docs for contributing.

FWIW, I use conda instead of virtualenv. So I was able to set up with

conda create -y -n cotede37 python=3.7
conda activate cotede37

instead of mkvirtualenv cotede.

After that, all steps were the same.

flake8 was not in the requirements list anywhere, so I added that to test-requirements.txt and added a step to install the libs in that file.

I was able to run the tests described:

$ flake8 cotede tests
$ py.test tests
$ tox

However there are a lot of flake8 failures. I recommend resolving those and/or adding a list of ignored tests to flake8-ignore. Otherwise, as a contributor I'd just ignore this.

Ref: openjournals/joss-reviews#2063

[castelao]

Thanks @jessicaaustin . CoTeDe has been available at conda for some time now. As I mentioned before, I removed the requirement on running flake8 for now and I've been slowly refactoring/re-organizing the code. Unfortunately, parts of the code pre-date black and flake8, but I'm working on that. Thank you.