Enable absolute imports, true division, & print()

These have no effect in Python 3.x, they are the default. Enabling them
in Python 2.x, enabling them in Python 2.x allows single source
compatiblity.

src/bindings/python/hammer_tests.py

@@ -1,3 +1,5 @@
+from __future__ import absolute_import, division, print_function
+
 import unittest
 import hammer as h