Add clipboard copy for code samples
Implement the "copy to clipboard" feature we have for code samples on the Nanoc site.
Things to note:
- The Nanoc version has Bootstrap as a dependency for tooltips (the "Copied!" text that comes up when you click the icons). We'll need to come up with a new way to do tooltips like these. Offhand I can't think of anywhere else we use these, but we should implement something generic enough that it could be used elsewhere
Edited by Sarah German