Simple document format

This is a major restructuring of the package embracing `rmarkdown` fully.  It has two main features,

1. fully support rmarkdown, building knitrBootstrap off of `html_document()`
2. simplify the code by removing features
  - style and code theme choosers
  - global toggles

It aims to do as little work in javascript as possible, namely no DOM restructuring (other than highlighting).