Fix pypy3, py3.7 and remove py33 (#99)

Author: kvesteri

.travis.yml

@@ -1,13 +1,15 @@
 language: python
-python:
-  - 2.7
-  - 3.3
-  - 3.4
-  - 3.5
-  - 3.6
-  - 3.7
-  - pypy
-  - pypy3
+matrix:
+  include:
+    - python: 2.7
+    - python: 3.4
+    - python: 3.5
+    - python: 3.6
+    - python: 3.7
+      dist: xenial
+      sudo: true
+    - python: pypy
+    - python: pypy3
 install:
   - pip install -e ".[test]"
 script:

setup.py

@@ -62,7 +62,6 @@ def get_version():
         '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',