Add support for Chapters and navigation

[allizad]

I'm starting to think about what content to add over the next month, but I need to separate this new content from the existing storyline, as a "next Chapter" link of "turning the page".

In order to add more chapters so that they're 'chunkable' for the user, we need to add some sort of navigation so people don't have to scroll forever. Would love to get with @jnymck to talk about what this could and should look like with some SketchUp examples.

Would also be cool to see if this could perhaps map to some sort of twitter sign-in and people could keep track of their learning progress.

At the very least we need to add routing and a server or generate static files. I like the idea of having a small app and we can start making more templates and DRY stuff up a bit on the HTML side. Open to thoughts!