Automatically reposition the Dim the Lights mask when the video position changes. Fixes #10.
use the schnur recursive timeout technique, and use a 500ms interval instead of 100ms
DTL: fix so that repositioning timeout is removed if video is removed from the page
Merge pull request #11 from wistia/bs-dim-the-lights-and-hello-bar

Automatically reposition the Dim the Lights mask when the video position changes