Add style sheet to html theme; fix issues

* add rudimentary style sheet to html theme for testing
* fix router to handle the 404 Not Found case better
* fix published_date to handle IOErrors when parsing files
* tweak static_url to not have a / at the end (need a better way to deal
  with this sort of thing across all config variables)
Fix compile to correctly copy static files

* fixes compile to correctly copy static files and create directories
* fixes serve to ignore static assets--they don't need rerendering;
  however this is annoying since it means you have to recompile every
  time you make js/css changes