Add note about optionally installing watchdog
Add note about optionally installing watchdog

kwangkim/landslide,ptisserand/landslide,kwangkim/landslide,ionelmc/python-darkslide,ionelmc/python-darkslide,kwangkim/landslide,adamzap/landslide,exciteresearch/landslide,exciteresearch/landslide,ionelmc/python-darkslide,ptisserand/landslide,adamzap/landslide,adamzap/landslide,exciteresearch/landslide,ptisserand/landslide