add github page handler

closes #8 

you can see the page in action here: 
http://shogun-web.herokuapp.com/shogun_readme

Its not linked from anywhere and I don't know if this is even a page we would want this for, that's a discussion for what should be on the homepage. This is a proof of concept for fetching a github markdown file and rendering it on our site.

cc @iglesias if you have any comments on naming or structure let me know, otherwise I will merge this shortly.