add a tox file

tox.ini

+[tox]
+envlist = py27,py3,flake8
+
+[testenv]
+deps =
+  mock
+  webtest
+  pytest
+commands =
+  {envpython} -m pytest {posargs}
+
+[testenv:flake8]
+skip_install = true
+deps =
+  flake8 >= 3.5
+commands =
+  {envpython} -m flake8 -- --exclude=*_Any.py
+