Upgrade jquery to version 1.8.

This required an upgrade to webshims as well. This upgrade is needed for the copy/paste plugin to handle math correctly, because jQuery.has() has a bug in version 1.7. This also puts gh-book and remix on the same version of jquery.

Merge https://github.com/oerpub/Aloha-Editor/pull/102 before you merge this, or else remix will stop working on chrome.