Add CHANGES line.

Author: Patrick Lawson

CHANGES.txt

@@ -5,6 +5,10 @@
 * Use environment markers to filter packages before determining if a
   required wheel is supported. Solves (:issue:`3254`).
 
+* Add --platform and --supported-interpreter-version parameters to ``pip download``.
+  These allow utilities and advanced users to gather distributions for interpreters
+  and platforms other than the ones pip is being run on.
+
 
 **8.1.1 (2016-03-17)**