Move XEP-0118 to the new system.

sleekxmpp/plugins/xep_0118/__init__.py

@@ -6,6 +6,11 @@
     See the file LICENSE for copying permission.
 """
 
+from sleekxmpp.plugins.base import register_plugin
+
 from sleekxmpp.plugins.xep_0118 import stanza
 from sleekxmpp.plugins.xep_0118.stanza import UserTune
-from sleekxmpp.plugins.xep_0118.user_tune import xep_0118
+from sleekxmpp.plugins.xep_0118.user_tune import XEP_0118
+
+
+register_plugin(XEP_0118)