Add feature to show/hide bits of a guide based on preferences

Add support for embedded CSS classes that allow hiding segments of a guide based on build systems. Embed these selections in a cookie so that preferences are carried across various guides.
Process comments and fix sidebar table of comments

* Fixed $(ready) thing
* Removed console.log statements
* Simplified conditional branch as requested
* Moved constants to top of module
* Simplified event handler by moving up to sagan-level container
* Changed reveal(cls) to tap hideBuildSteps() for removing CSS ops
* Altered generation of sidebar content, so it finds any links associated with .reveal-foo, and trims them out of the sidebar.
* Move docCookie into separate module
Use localStorage instead of cookies

localStorage is widely supported:
http://caniuse.com/#feat=namevalue-storage
Merge pull request #1 from bclozel/gregturn-hide-show-guide

Use localStorage instead of cookies
Merge pull request #454 from gregturn/hide-show-guide

Add feature to show/hide bits of a guide based on preferences