fix duration for jwplayer
Make duration a local variable
Clean up comments
make sure to set player as ready after duration is available
Allow multiple sources for JW player
Assume that metadata about the video is available when duration is available
Add more meaningful commnets
Merge pull request #420 from ilyakatz/jwplayer_duration_fix

Jwplayer duration fix
Merge pull request #421 from ilyakatz/multiple_sources_for_jwplayer

Allow multiple sources for JW player