curds: Use sort keys for inserting playlist nodes

This is slower, but puts things in their right place. Implementing a
bisect search should help speed this up.

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

curds/playlist/node.py

@@ -77,7 +77,7 @@ class PlaylistNode:
 
     def insert_child(self, child):
         for i, n in enumerate(self.children):
-            if child < n:
+            if child.sort_key() < n.sort_key():
                 return self.__insert_node__(child, i)
         return self.append_child(child)