Upgrade jQuery to 1.8.3.

I tested out Guiders 1.3.0 against this with one of the demos.  Also, Wikimedia is using [our fork](https://github.com/wikimedia/mediawiki-extensions-GuidedTour-guiders) with this version of jQuery.  Although we have some unrelated changes, we didn't have to do anything to make it work with this version of jQuery.