[Summon 2] Cleanup, add support for individual pages

Detection on multiples should be broken now, because it requires monitorDOMChanges, which makes the page unusable right now.
Test doesn't actually work on the "book" item, for unknown reasons. Possibly because offsetHeight is not set in a hidden iframe? (making this up)

Please do take this for a spin. I'd say enable the commented out `monitorDOMChanges`, which makes detection work very well while navigating the page, but it really slows down to a halt fast.