Use floor division for python3 compatibility

[rev138]

As noted in #20, the randint() method incorrectly returns floats in python 3, due to changes in the behavior of the division operator. This PR uses "floor division" to ensure integer results (see: https://docs.python.org/3/glossary.html#term-floor-division)

[catchthemonster]

Hi, is this fixed as I am still getting in py3 floats!!