update change notes for medusa

supervisor/medusa/CHANGES.txt

@@ -3,6 +3,7 @@ PATCHES MADE ONLY TO THIS MEDUSA PACKAGE BUNDLED WITH SUPERVISOR
   and updated Medusa throughout to use these.  The Python 2.6 stdlib version
   of these modules introduced backward-incompatible changes.
 * Changed imports throughout from "medusa" to "supervisor.medusa".
+* Removed medusa files not used by Supervisor.
 
 Version 0.5.5: