Travis CI: Add Python 3.6 and 3.7 to the testing

Author: cclauss

.travis.yml

@@ -3,11 +3,15 @@ python:
   - "2.7"
   - "3.4"
   - "3.5"
+  - "3.6"
   - "pypy"
   - "pypy3"
 sudo: false
 matrix:
   fast_finish: true
+  include:
+    - python: "3.7"
+      dist: xenial  # required for Python >= 3.7 (travis-ci/travis-ci#9069)
 
 install:
   - pip install wheel tox-travis

tox.ini

@@ -4,5 +4,5 @@ envlist = py27, py34, py35, pypy, pypy3
 [testenv]
 deps = -r{toxinidir}/tests/requirements.txt
 commands =
-    flake8
+    flake8 --ignore=E741,W605
     nosetests