Added Python 3 support to setup.py
Added Python 3 support to setup.py

Ticket #150 and commit 2f71d6621d7d1d7fe733488f09d23533c772c849 indicate that watchdog now supports Python 3.

This change updates the setup.py so that the next PyPI release will be properly marked as Python 3 compatible.
glorizen/watchdog,ymero/watchdog,teleyinex/watchdog,ymero/watchdog,gorakhargosh/watchdog,mconstantin/watchdog,glorizen/watchdog,ymero/watchdog,teleyinex/watchdog,glorizen/watchdog,mconstantin/watchdog,mconstantin/watchdog,gorakhargosh/watchdog,teleyinex/watchdog