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?
The “and other properties” seems odd here. Since this is an upgrade guide I'd like every affected property out. I'd also give a quick before/after example here too.