Issue title: Add CONTRIBUTING.md
 Issue body: For the same reasons as https://github.com/openhatch/oh-mainline/issues/1560
 Comments: 
 Comment 0: :+1:
 Comment 1: @pdurbin Are you waiting for me to do this or am I waiting for a PR from you? :)
 Comment 2: @prologic I think you should write it up since you'll know best how people can effectively contribute.
 Comment 3: Okay :)


James Mills / prologic

E: gutierrezcheryl@example.com
W: prologic.shortcircuit.net.au

On Sun, Apr 19, 2015 at 10:30 PM, Philip Durbin <gutierrezcheryl@example.com>
wrote:

> @prologic <https://github.com/prologic> I think you should write it up
> since you'll know best how people can effectively contribute.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/circuits/circuits/issues/14#issuecomment-94271348>.
>

 Comment 4: Came across [CONTRIBUTING.md](http://contribute.md/)

Going to use this as a template :)
 Comment 5: @pdurbin @spaceone @y0no Any thoughts on this? Feedback? :)
 Comment 6: See PR #71 
 Comment 7: I'm okay with that
 Comment 8: :+1: 
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