expunge python 2.6 (#3962)

* expunge python 2.6

* how did THAT happen

* remove another unsupported python from the tox envlist

* hypothesis can now be unconditionally imported
diff --git a/README.rst b/README.rst
index 350dc72..1557666 100644
--- a/README.rst
+++ b/README.rst
@@ -18,7 +18,7 @@
 
 ``cryptography`` is a package which provides cryptographic recipes and
 primitives to Python developers.  Our goal is for it to be your "cryptographic
-standard library". It supports Python 2.6-2.7, Python 3.4+, and PyPy 5.3+.
+standard library". It supports Python 2.7, Python 3.4+, and PyPy 5.3+.
 
 ``cryptography`` includes both high level recipes and low level interfaces to
 common cryptographic algorithms such as symmetric ciphers, message digests, and