Returns Weed-FS master version

        :rtype: string

def version(self):
        '''
        Returns Weed-FS master version

        :rtype: string
        '''
        url = "http://{master_addr}:{master_port}/dir/status".format(
            master_addr=self.master_addr,
            master_port=self.master_port)
        data = self.conn.get_data(url)
        response_data = json.loads(data)
        return response_data.get("Version")