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?
This is just the overview, there are detailed examples for everything below. I can look into linking to those, though if it didn't look to you like a summary, maybe I should just drop it instead. Thoughts?