"Open in Youtube" feature

fixes #7 
Please move this part under https://github.com/JoseRoman/Atraci/blob/master/coffee/_tracklist.coffee#L95

Reasons : 

1. Don't put this into $.each, otherwise you will get more than one `open in youtube` menuItem if your number of playlists is more than one.

2. This menuItem should be standalone and put at the bottom of the menu. Because we may add `Remove from xxx` menuItem, the safe way for `Open in Youtube` menuItem is to make it at the bottom.