Assertion methods clean-up from Global and QUnit.constructor scopes

I know that the commit names aren't the best, but I'm probably going to squash @74dbc94, @505a3b9 and @6b4876d, so I'm letting these for review purposes.

The patch is basically done and there's a lot of tests, maybe you want to remove some, and I'll agree. :)

Fixes #563
`QUnit.test`