Upgrade to Bootstrap 3.2.0, keep track of CSS changes

* while upgrading, change some more Bootstrap Less variables and record
  them in a .txt file for reference
Update _config.yml "highlighter: pygments"

Jekyll complains about a deprecation warning. That's all.
Add 'factorize' and related scaffolding

* Let front matter specify 'extracss' and 'extrajs' to include in the
  default layout
* Add trivial JavaScript factorizer, ported from other places to
  CoffeeScript