Retry stalled asset downloads in HTML.
Retry stalled asset downloads in HTML.

Which seems to happen occassionally on mobile browsers. This
periodically checks if the last progress event is more than 5 seconds
old, and if so, aborts and retries up to a total of 4 attempts.

Closes #14.

aduros/flambe,mikedotalmond/flambe,playedonline/flambe,markknol/flambe,markknol/flambe,playedonline/flambe,playedonline/flambe,weilitao/flambe,Disar/flambe,markknol/flambe,mikedotalmond/flambe,aduros/flambe,Disar/flambe,playedonline/flambe,aduros/flambe,weilitao/flambe,weilitao/flambe,Disar/flambe,weilitao/flambe,aduros/flambe,Disar/flambe,mikedotalmond/flambe,mikedotalmond/flambe