Add urllib3 transport (#14)

diff --git a/tests/transport/compliance.py b/tests/transport/compliance.py
index ad4e491..6d2a304 100644
--- a/tests/transport/compliance.py
+++ b/tests/transport/compliance.py
@@ -25,7 +25,7 @@
 
 class RequestResponseTests(object):
 
-    @pytest.fixture
+    @pytest.fixture(scope='module')
     def server(self):
         """Provides a test HTTP server.