Drop support for Python 3.3; add support for 3.6.

CHANGES.txt

 ``zodburi`` Changelog
 =====================
 
-2.2.3 (unreleased)
+2.3.0 (unreleased)
 ------------------
 
-- TBD
+- Drop support for Python 3.3.
+
+- Add support for Python 3.6.
 
 2.2.2 (2017-05-05)
 ------------------

setup.py

@@ -27,7 +27,7 @@ docs_extras = tests_require + [
 ]
 
 setup(name='zodburi',
-      version='2.2.3.dev0',
+      version='2.3.0.dev0',
       description=('Construct ZODB storage instances from URIs.'),
       long_description=README + '\n\n' +  CHANGES,
       classifiers=[
@@ -36,9 +36,9 @@ setup(name='zodburi',
         "Programming Language :: Python :: 2",
         "Programming Language :: Python :: 2.7",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.3",
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
+        "Programming Language :: Python :: 3.5",
         "License :: Repoze Public License",
         ],
       keywords='zodb zodbconn',

tox.ini

 [tox]
 envlist =
-    py27,py33,py34,py35,cover,docs
+    py27,py34,py35,py36,cover,docs
 
 [testenv]
 commands =