Fix tests

$ python2.7 EulerPy/tests.py
...
----------------------------------------------------------------------
Ran 3 tests in 0.198s
OK
$ python3.2 EulerPy/tests.py
...
----------------------------------------------------------------------
Ran 3 tests in 0.270s
OK
$ python2.6 EulerPy/tests.py
...
----------------------------------------------------------------------
Ran 3 tests in 0.232s

OK