New CONTRIBUTING.md

[riverma]

Purpose

• A contributing guide to help establish project wide standards for contribution

  Proposed Changes

• [ADD] A new contributing guide

Issues

• N/A

  Testing

• In-development

[sjlewis-jpl]

@riverma - I made a bunch of edits to CONTRIBUTING.md, have a look when you get a chance. I removed a few sections, and reorganized it a bit. The main content that I worked on is all under the last section, "Development Guides".