add a contributing document

text is pulled out of the wiki.  This will enable github to show a link when
a contributor creates an issue or opens a Pull Request

CONTRIBUTING

@@ -0,0 +1,24 @@
+Go to http://gitolite.com/gitolite/index.html#contact for information on
+contacting me, the mailing list, and IRC channel.  *Unless you are reporting
+what you think is a security issue, I prefer you send to the mailing list,
+not to me directly.*
+
+Please DO NOT send messages via github's "issues" system, linkedin
+comments/discussion, stackoverflow questions, google+, and any other Web 3.0
+"coolness". (The issues system does have an email interface, but it is not a
+substitute for email. I can't cc anyone else when I want to, for instance.
+Well I can, but any response the original requester then makes using the
+website will not get cc-d to the person I cc-d).
+
+Please send patches *via email*, not as github pull requests. Again, if you
+think it's a security issue, send it directly to my gmail address, but
+otherwise please send it to the mailing list, so others can see it and comment
+on it.
+
+The preferred format is the files created by git-format-patch, as attachments.
+However, if your repo has a public clone URL, you can make a new branch just
+for this fix, and send the repo URL and branch name to the mailing list.
+
+(If you do send me a github pull request, I may take it if it's a trivial
+patch, but otherwise I'll ask you to close the pull request, then read
+this URL for how to send me the patch.)