Joins a new channel.

        Keyword arguments:
        new_channel: <str>; the channel to connect to
        nick: <str>; the nickname to use
        pwd: <str>; the (optional) password to use

def join(self, new_channel, nick, pwd=None):
        """Joins a new channel.

        Keyword arguments:
        new_channel: <str>; the channel to connect to
        nick: <str>; the nickname to use
        pwd: <str>; the (optional) password to use
        """
        self._send_packet({"cmd": "join", "channel": new_channel,
                           "nick": self._format_nick(nick, pwd)})