In order to use this plugin, its config values need to be properly
setup. supybot.plugins.Limiter.enable needs to be set to True and
supybot.plugins.Limiter.{maximumExcess,minimumExcess} should be set to
values appropriate to your channel (if the defaults aren't satisfactory).
Once these are set, and someone enters/leaves the channel, Supybot will
start setting the proper +l modes.