This PR updates Bootstrap and CodeMirror, and finally fixes the width of the sidebar. It should be of flexible width now, sizing with the width of the nav items’ text. @jashkenas, please let me know what you think. https://rawgit.com/GeoffreyBooth/coffeescript/docs-improvements/docs/v2/

This PR incorporates the minor changes I made on #5035 aside from adding the fulltext search.