Add CONTRIBUTING.md file

[MrPowers]

Add a CONTRIBUTING.md file, so other devs know how to contribute to this project.

[dennyglee]

Reference: https://github.com/delta-io/delta/blob/master/CONTRIBUTING.md

[irfanghat]

Hi @MrPowers, @dennyglee, I’d like to work on this. The Delta Lake guide you linked should provide a solid reference. I’ll use it to draft a CONTRIBUTING.md with setup instructions, coding standards, and contribution steps. Let me know if there’s anything specific, you’d like to include.

[dennyglee]

Sure, by all means @irfanghat - including @rtyler and @roeap on what they think as well, eh?!

[irfanghat]

Hi @dennyglee, @MrPowers, I created a PR here - #219
Please let me if there's anything that needs to be changed, I tried to reference other repos under delta