curds: Make it easier to send the playlist-changed notification

We're going to use this to notify that the current playlist has been
changed

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/playlist/playlist.py

@@ -39,6 +39,9 @@ class Playlist():
         if track is not None and track not in self:
             self.list.append(track)
             notify.notify("add-track", self, track, self.list.index(track))
+            self.changed()
+
+    def changed(self):
             notify.notify("playlist-changed", self)
 
     def next(self):