Ah. We're finally good for Firefox, IE9, Chrome; a messy one again … grrr:

 * to get respond.js actually working (to support Bootstrap grids in IE8), we of course need it locally – which means we also need Bootstrap's CSS and Glyphicon fonts locally … goodbye CDN :(
   * there's a "copy_docs_assets" taks to the Makefile to copy Bootstrap's CSS and font-directory plus respond.js over to _jekyll
 * while we're at it:
   * bump sass-bootstrap to latest commit from 3.0.0-wip
   * introduce "js"- and "css"-folders in _jekyll
   * add html5shiv

 * add examples for input group buttons with dropdowns
 * remove prepended+appended input group example for now