Support Python 3.7, drop 3.3 (DataDog#345)

Author: ofek

.travis.yml

@@ -19,6 +19,8 @@ matrix:
       env: TOXENV=py35,flake8
     - python: 3.6
       env: TOXENV=py36
+    - python: 3.7
+      env: TOXENV=py37
     - python: pypy
       env: TOXENV=pypy
       # PyPy isn't yet available on Xenial

setup.py

@@ -49,10 +49,10 @@ def get_readme_md_contents():
         "License :: OSI Approved :: BSD License",
         "Operating System :: OS Independent",
         "Programming Language :: Python :: 2.7",
-        "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",
         "Programming Language :: Python :: Implementation :: PyPy",
     ]
 )

tox.ini

@@ -2,7 +2,7 @@
 minversion = 3.7.0
 skip_missing_interpreters = true
 envlist =
-    py{27,33,34,35,36,py}
+    py{27,34,35,36,37,py}
     flake8
 
 [testenv]