Add future imports for with statement use in tests

test/test_algorithm.py

 #! /usr/bin/env python
 
+from __future__ import division, with_statement
+
 __copyright__ = "Copyright (C) 2013 Andreas Kloeckner"
 
 __license__ = """

test/test_array.py

 #! /usr/bin/env python
-from __future__ import division
+from __future__ import division, with_statement
 
 __copyright__ = "Copyright (C) 2009 Andreas Kloeckner"