Add Code of Conduct to site

This adds a http://codeforportland.org/code-of-conduct page and a link to it in the header. I think it's important to make this more prominent ahead of a big event like NDoCH. I also changed the contact info in the code of conduct to info@codeforportland.org, which forward to the organizers mailing list so that all organizers will be made aware of an issue and there is no single point of failure in terms of communication and taking responsibility for whatever situations may arise. The main gist: don't be a jerk!

Thanks all.