Tests: Replace resource loader with AMD

:boom: WIP...

Pulll request's goal is to AMDify tests for 1.12.0 release and address part of http://bugs.jqueryui.com/ticket/10119.


Just seems like we shouldn't have to maintain our own css injector that uses `document.write` when `require` has a good one. I'd avdocate for either including the css with no js to handle writing the link tags, or use require to load the css.