Correctly uninvert YouTube previews
Fix inversion of dynamic iframes

This includes Twitter previews on certain sites.

Fixes issue #34
Improve popup description logic

The changes made for the dim slider slightly altered the logic used by
the popup to display what scheme is in use. Restore that part of the
logic to the old behavior.
Fix inverted images in Hangouts app

When Chrome is configured to allow extensions access to chrome:// URLs,
this extension can get injected into some Chrome apps (like Hangouts).
Update the injection logic to not always assume Deluminate has been
injected into the topmost window, and supply a fallback to checking the
tab URL (apps don't have a real tab) with the window's baseURI.
Fix icons in Google groups
Invert PDFs in Gmail and elsewhere