Improve how documentation content is presented #344

We have good content in this repo, but I think it could be easier to absorb and navigate if its presentation was improved.

I like what ReasonML does for their docs, and propose we adopt some of their strategies:

• A concise overview page of short examples, with a "details" link to each topic for a deeper explanation.
• Presented on a dedicated webpage with a navigation sidebar. This is much nicer to use than clicking through a tree of files on github.
• A smart search feature with prioritized results.