Add CONTRIBUTING.md

[CDKnightNASA]

Is your feature request related to a problem? Please describe.
github repositories are suggested to have a CONTRIBUTING.md document which describes best practices for developers wishing to contribute to the main release.

Describe the solution you'd like
Develop a CONTRIBUTING.md document with simple stuff like "follow the coding style guidelines", run unit tests prior to a pull request, etc.

Describe alternatives you've considered
Likely will need to incorporate or reference existing documentation. Could also use the wiki capabilities of dropbox.

Additional context
Add any other context about the feature request here.

Requester Info
Chris Knight, NASA Ames Research Center.

[skliper]

Fixed by #1227