Start a thread for each registered scan function to scan proxy lists

def scan(self):
        """Start a thread for each registered scan function to scan proxy lists"""
        self.logger.info('{0} registered scan functions, starting {0} threads '
                         'to scan candidate proxy lists...'
                         .format(len(self.scan_funcs)))
        for i in range(len(self.scan_funcs)):
            t = threading.Thread(
                name=self.scan_funcs[i].__name__,
                target=self.scan_funcs[i],
                kwargs=self.scan_kwargs[i])
            t.daemon = True
            self.scan_threads.append(t)
            t.start()