Drop support for Python 3.3

Author: johnthagen

setup.py

@@ -29,7 +29,6 @@
         '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 :: 3.6',

tox.ini

@@ -2,7 +2,6 @@
 # Environment changes have to be manually synced with '.travis.yml'.
 envlist =
     py27
-    py33
     py34
     py35
     py36