Pages: Upgade guide to QUnit 2.x

Fixes #86 

First draft for an upgrade guide. There are no links to this page, yet. There are layout issues, may need to port some CSS from jqueryui.com.

Would be good to get some feedback on the format. Also, am I missing something?
Huh, I see that you have examples but that they're later on in the document. Personally I'd combine the two sections, as I had no idea to look further down.