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?
I would use the `QUnit.log` as the first example, so the reader can catch it sooner, even reporters might rely more on QUnit.done.