Add Codio Walkthrough

Copied from the blog post. https://duck.co/blog/codio-duckpan What do you guys think?
Not really related to this PR but I think it's safe to give Mac OS the OK seeing as we haven't had any reported OSX issues in a while. I had no problems installing it on my machine and as we recently were notified on the DDH mailing list, it seems like the install was fine for OSX 10.8-10