Track py.test 1.0 marker changes.

pytools/test.py

 try:
     from py.test import mark as mark_test
 except ImportError:
-    def mark_test(**kwargs):
-        def dec(f):
-            return f
-        return dec
+    class _Mark:
+        def __getattr__(self, name):
+            def dec(f):
+                return f
+            return dec
+    mark_test = _Mark()