Update CHANGES for 0.4.1

Author: tony

CHANGES

@@ -4,6 +4,10 @@ Changelog
 
 Here you can find the recent changes to libtmux
 
+- :release:`0.4.1 <2016-05-23>`
+- :support:`-` update ``which()`` to find tmux via ``os.environ['PATH']``.
+  https://redd.it/4laeut
+
 - :release:`0.4.0 <2016-05-23>`
 - :support:`-` attributes for formatters are now accessible via
   ``Session``, ``Window`` and ``Pane`` objects. ``session.name``