chore: get the specs to run in MSIE

[coreyti]

At the very least, need to do the frame.contentDocument || frame.document check.

[coreyti]

It turns out, the major issue with running the specs in MSIE is, the iframe document's "ready state" is "loading", and does not reach "complete" until after the specs have run. Not sure how best to handle this (other than switching to an asynchronous-capable version of Screw.Unit).