Add Python 3.7 and Windows to Travis-CI (#34)

* Add Python 3.7 and Windows to Travis-CI

* Reorder environments

tox.ini

@@ -1,11 +1,17 @@
 [tox]
-envlist = py27,py34,py35,py36
+envlist = py27,py34,py35,py36,py3-win
 skip_missing_interpreters = True
 
 [testenv]
+platform = linux
 commands =
     python setup.py test
 
+[testenv:py3-win]
+platform = win
+commands =
+    python setup.py test --test-suite tests.test_plat_win
+
 [testenv:py27]
 deps =
     configparser