NOISSUE - Add CONTRIBUTING.md file, containing a proposal for

[jmcconnell26]

contributing to the project

[anderejd]

Looks good to me, let's leave this open for a while to get some feedback.

[Shnatsel]

I'm not convinced that signing commits is a good idea, since it increases the entry barrier for contributions and does not accomplish much without a solid identity management layer on top of it. I suggest making it optional rather than required.

[tarcieri]

It also provides dubious security value until git migrates away from SHA-1, which is cryptographically broken.

[anderejd]

Thanks for the feedback!

I agree that the entry barrier should be low, I have added emphasis using bold styling for the following sentence: "Pull requests are very welcome, and the below are guidelines, not rules."

I'll remove the point about commit signing in the document.