added more steps to contributing docs

[screwed99]

What does this PR do?

Adds more steps to contributing documentation, see issue #134.

Where should the reviewer start?

Only made changes to contributing.md

How should this PR be tested?

I've used mkdocs serve to see changes locally

Any background context you want to provide?

Had to do some rejigging of the text due to the numbered list in that section getting broken up otherwise. Also note that I don't think you've deployed new documentation to Github on your repo since your recent commit on how to use mkdocs.

What are the relevant issues?

Solves issue #134.

[coveralls]

Coverage remained the same at 28.706% when pulling 1e6d9f8 on screwed99:contr-docs into 8417028 on rhiever:master.

[rhiever]

Thanks again! :-)

[screwed99]

Hey, not exactly sure where is best to message you about this but what would you advise as a next step for contributing to TPOT? I'm looking at issue #129 which doesn't seem to have anyone working on it currently while also seeming like it won't require any major code restructuring.

I am also confused about the ongoing PR #126 with unit tests being added, it appears you are waiting for something before you merge it with the rest of the code. Not sure where this leaves me in terms of wanting to help adding tests.

Do you have any thoughts?

[rhiever]

#129 looks like a great PR to work on! I don't think anyone has been working on that one.

Just to make sure: @teaearlgraycold, what issues are you working on this week?

#126 is an ongoing project that I'm working on with a student for the next couple weeks. I've just merged the PR since all the unit tests look fine. If any of your changes affect those unit tests, please make sure to update them.

Cheers!