Changes:

* Intermittent scrollbar visibility bug fixed. This change introduces a
  backwards incompatible change to the theme's layout HTML. This should only be
  a problem for derivative themes that have overridden styling of nav elements
  using direct decendant selectors. See #215 for more information.
* Safari overscroll bug fixed
* Version added to the nav header
* Revision id was added to the documentation footer if you are using RTD
* An extra block, ``extrafooter`` was added to allow extra content in the
  document footer block
* Fixed modernizr URL
* Small display style changes on code blocks, figure captions, and nav elements