curds: Move playlist previous() function out of Root

And into the package init file

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

curds/playlist/__init__.py

@@ -31,7 +31,7 @@ def next():
 def previous():
     global Track
     with Lock:
-        Track = Root.previous()
+        Track = Root.lookup("Previous").next()
         return Track
 
 def save():

curds/playlist/root.py

@@ -74,9 +74,6 @@ class PlaylistRoot(node.PlaylistNode):
             random.setstate(state)
             return res
 
-    def previous(self):
-        return self.lookup("Previous").next()
-
     def reset(self):
         with self.node_lock:
             for plist in self.children:

curds/playlist/test_root.py

@@ -130,7 +130,7 @@ class TestPlaylistRoot(unittest.TestCase):
         self.assertEqual(prev[0], track2)
         self.assertEqual(prev[1], track1)
 
-        self.assertEqual(self.playman.previous(), track1)
+        self.assertEqual(self.playman.lookup("Previous").next(), track1)
         self.assertEqual(self.cb_track, track2)
 
         self.playman.reset()