don't show song name after iTunes quits

iTunes 11 no longer posts a "Stopped" notification before it quits.
Fixed by listening to app-terminated notifications and clearing the song
info when iTunes quits.

The menu also fetches the version number from the bundle instead of
using a hardcoded string in the nib.
version 1.1

Updated to work better with iTunes 11; the last-playing song no longer
continues to display after iTunes quits.