Add tox config

tests/test_shells.py

@@ -75,4 +75,4 @@ class TestZsh(object):
                      return_value=1430707243.3517463)
         shells.Zsh().put_to_history('ls')
         builtins_open.return_value.__enter__.return_value. \
-            write.assert_called_once_with(': 1430707243:0;ls\n')
+            write.assert_called_once_with(': 1430707243:0;ls\n')

tox.ini

@@ -0,0 +1,6 @@
+[tox]
+envlist = py27,py33,py34
+
+[testenv]
+deps = -rrequirements.txt
+commands = py.test