Mechanize default theme updating

[jonocodes]

Figure out a way to keep up to date with upstream Jekyll theme better. Right the default theme file is generated by me viewing one of the rendered classroom documents. For example:
http://training.play-with-docker.com/helloworld/

I copy the HTML, then modify it to my needs. This means stripping out the header and footers, removing some scripts and DOM elements that are not needed. Then I add back some of the templating from
https://github.com/play-with-docker/play-with-docker.github.io/blob/master/_layouts/post.html

This is not efficient. There should either be a way of automating this, or at least a document that says exactly how to do this for future updates to the theme.

Additionally we should pull down copies of static assets like pwd.js and the css. Right now we are just referencing them from their original hosts, but since thats a moving target it is more brittle then having our own copy. We can host these right out of pwder by creating a route for static assets in Sinatra.

[jonocodes]

started a doc here https://github.com/jonocodes/pwder/wiki/Templates