Drop support for Python 3.3, and add 3.7

Author: userzimmermann

.travis.yml

@@ -3,10 +3,10 @@ sudo: false
 language: python
 python:
   - '2.7'
-  - '3.3'
   - '3.4'
   - '3.5'
   - '3.6'
+  - '3.7'
   - pypy
 
 install:

setup.py

@@ -41,10 +41,10 @@
         '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',
+        'Programming Language :: Python :: 3.7',
         'Topic :: Software Development',
         'Topic :: Utilities',
     ],

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py33,py34,py35,py36,pypy
+envlist = py27,py34,py35,py36,py37,pypy
 
 [testenv]
 deps =