Fixed #3334 -- added Python 3.6 support (#3335)

* Fixed #3334 -- added Python 3.6 support

* install py36

* empty commit to retrigger travis

* this is an impressively dumb typo
diff --git a/docs/installation.rst b/docs/installation.rst
index 0c489ad..888b8bc 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -10,8 +10,8 @@
 Supported platforms
 -------------------
 
-Currently we test ``cryptography`` on Python 2.6, 2.7, 3.3, 3.4, 3.5, and PyPy
-2.6+ on these operating systems.
+Currently we test ``cryptography`` on Python 2.6, 2.7, 3.3, 3.4, 3.5, 3.6, and
+PyPy 2.6+ on these operating systems.
 
 * x86-64 CentOS 7.x, 6.4
 * x86-64 FreeBSD 10