Create CONTRIBUTING.md -- document procedure

[jGaboardi]

This PR:

• resolves Add contributing guidelines document #4
• kicks off potential testing schema #7 – gives a structure, but we can work on ironing out the wording if needed. I welcome input on language, other sections, etc.

[jGaboardi]

Let's wait for @anastassiavybornova to read/review to see if she has any suggestions.

[anastassiavybornova]

looks good to me! but we do plan to make the contributing guidelines more detailed than this, right? (otherwise my comment would be "should be more detailed" 😄 )

[martinfleis]

I like this template https://clustergram.readthedocs.io/en/stable/contributing.html but that can wait.

[jGaboardi]

we do plan to make the contributing guidelines more detailed than this, right?

Yes, this is merely a first pass to get it started

I like this template https://clustergram.readthedocs.io/en/stable/contributing.html but that can wait.

I'll open a new issue where we can discuss how to flesh out further.