Adding trove classifiers so it's easier to check for Python 3 compatability.

Various tools including Django Packages rely on trove classifiers for this sort of thing. Since this is passing the Python 3 tests, I added in the extra specifics. Please include this in the next formal release!
Merge pull request #247 from pydanny/patch-1

Adding trove classifiers so it's easier to check for Python 3 compatability