port 2.1.1 changelog (#3975)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index b4ca5ac..fc0e8bf 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -10,6 +10,13 @@
 
 * **BACKWARDS INCOMPATIBLE:** Support for Python 2.6 has been dropped.
 
+.. _v2-1-1:
+
+2.1.1 - 2017-10-12
+~~~~~~~~~~~~~~~~~~
+
+* Fixed support for install with the system ``pip`` on Ubuntu 16.04.
+
 .. _v2-1:
 
 2.1 - 2017-10-11