Change sys to os lib for win detection.

Author: drvinceknight

axelrod/__init__.py

@@ -1,7 +1,7 @@
 from __future__ import absolute_import
-import sys
+import os
 
-on_windows = sys.platform.startswith("win")
+on_windows = os.name == 'nt'
 
 # The order of imports matters!
 from .actions import Actions, flip_action

axelrod/tests/unit/test_windows_detection.py

@@ -1,16 +1,16 @@
 import unittest
-import sys
+import os
 import axelrod
 
 class TestWindowsDetection(unittest.TestCase):
 
-    @unittest.skipIf(sys.platform.startswith("win"),
+    @unittest.skipIf(os.name == 'nt',
                      "Skip this test if on windows")
     def test_detection_on_not_windows(self):
         """Test when not on windows"""
         self.assertFalse(axelrod.on_windows)
 
-    @unittest.skipIf(not sys.platform.startswith("win"),
+    @unittest.skipIf(os.name != 'nt',
                      "Skip this test if not on windows")
     def test_detection_on_not_windows(self):
         """Test when on windows"""