Add testing and document support for Python 3.7

Python 3.7 was released on June 27, 2018.

https://docs.python.org/3/whatsnew/3.7.html

Author: jdufresne

.travis.yml

@@ -14,8 +14,10 @@ matrix:
       env: TOXENV=py35
     - python: 3.6
       env: TOXENV=py36
-    - python: nightly
+    - python: 3.7
       env: TOXENV=py37
+      dist: xenial
+      sudo: true
     - python: pypy
       env: TOXENV=pypy
     - python: 3.5

setup.py

@@ -57,6 +57,7 @@ def get_long_description():
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: PyPy',
         'Topic :: Software Development :: Libraries :: Python Modules',

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py27, py34, py35, py36, pypy, pypy3, jython
+envlist = py27, py34, py35, py36, py37, pypy, pypy3, jython
 skipsdist = True
 skip_missing_interpreters = True