added ssl kwarg to setup.dancefloor

Supporting SSL:

    >>> from waltz import setup
    >>> urls = ('/', 'Index')
    >>> app = setup.dancefloor(urls, globals(), ssl=('/ssl/cert.crt', '/ssl/key.pem'))
    >>> class Index:
    ...    def GET(self):
    ...        return "serving https, ssl"
    ...
    >>> if __name__ == "__main__":
    ...    app.run()