Add Supervisor 3.2.1 release date to Supervisor 4 changelog

CHANGES.txt

@@ -31,6 +31,9 @@
 - Files included via the ``[include]`` section are now logged at the ``INFO``
   level instead of ``WARN``.  Patch by Daniel Hahler.
 
+3.2.1 (2016-02-06)
+------------------
+
 - Fixed a server exception ``OverflowError: int exceeds XML-RPC limits`` that
   made ``supervisorctl status`` unusable if the system time was far into the
   future.  The XML-RPC API returns timestamps as XML-RPC integers, but