Improve contenteditable detection
Fix #309: Autofocus prevention is broken

Autofocus was broken by some Firefox update, possibly version 29. This
commit fixes it again. It also fixes a bug where autofocus was prevented
even on blacklisted sites, and cleans the code a bit.
Remove old VimFxFindInput CSS
Cleanup CSS a bit
Raise the z-indexes used to trump youtube

Youtube uses 1999999999 as z-index for its top bar, which is a lot
higher than VimFx used for the help dialog and markers. This caused the
top bar to overlap the help dialog, and, more importantly, the markers,
making it impossible to see the marker for the search box, for example.

This commit raises VimFx’s z-indexes to trump Youtube.
Remove stray `console.log`s
Merge pull request #322 from lydell/fix-autofocus

Fix autofocus
Version bump and changelog update
Build version 0.5.11