Add some tests using tox

tox.ini

@@ -0,0 +1,34 @@
+[tox]
+envlist=
+    py27-django17,
+    py27-django18,
+    flake8,
+
+[flake8]
+max-line-length=100
+exclude=migrations
+
+[base]
+deps =
+    -r{toxinidir}/requirements-dev.txt
+
+[testenv]
+commands=py.test --tb native {posargs:tests}
+
+[testenv:py27-django17]
+basepython=python2.7
+deps =
+    Django>=1.7,<1.8
+    {[base]deps}
+
+[testenv:py27-django18]
+basepython=python2.7
+deps =
+    Django>=1.8,<1.9
+    {[base]deps}
+
+[testenv:flake8]
+basepython=python
+deps=flake8
+commands=flake8 {toxinidir}/cas_server
+