Ruby/Middleman -> Clojure/Stasis

This change pushes all changes from the previous kouphax/briefcase
repository aimed at rewriting the existing middleman site in clojure
using the stasis library.

Other significant changes include

- Content no longer broken into articles, screencasts, talks etc.
  Everything is organised as a single stream
- Content is tidied up with old yaml frontmatter settings removed
- Embedded gists are no longer embedded and have been moved out to
  normal syntax highlighted blocks
- Additional atome feeds added per category
- Additional category index page
- Pushes are still done through travis
- Static pages are no longer Jade.  Where necessary they are pure
  markdown (like index.md) and others they are data driven yaml files
  (testimonial, background).  This means in future we may generate
  different formats for them (PDF for example)

Expect failure.