Add note that python-meld3 package may be usable. Closes #596

setup.cfg

@@ -6,6 +6,11 @@ exclude=medusa
 nocapture=1
 
 [bdist_rpm]
+;If you are building your own RPM of Supervisor, it is recommended that you
+;also build your own RPM of meld3 (https://github.com/Supervisor/meld3) to
+;ensure you have the most recent version.  Your distribution may have a
+;"python-meld3" package that you might be able substitute here, but it may
+;not be compatible and may not have the most recent bug fixes.
 requires = 
   meld3