Put the URL with the Custom Build ID in the generated source files

Created by: potch

The new site has the awesome customization screen, but unless you manage your bookmarks like a champ, there's no clear mapping between which custom builds on your system correspond to which URLs on the site. It would rock socks if the URL of the custom build was in the header comment in the generated source files.

For example, In bootstrap.css, you could have something like:

/*!
 * Bootstrap v3.0.0
 * Custom build generated by http://getbootstrap.com/customize/?id=6277349
 *