base class for all rbot plugins certain methods will be called if they are
provided, if you define one of the following methods, it will be called as
appropriate:
called for a PRIVMSG if the first word matches one the plugin register()d
for. Use m.plugin to get that word and m.params for the rest of the
message, if applicable.
return a help string for your module. for complex modules, you may wish to
break your help into topics, and return a list of available topics if
topic is nil. plugin is passed containing the matching
prefix for this message - if your plugin handles multiple prefixes, make
sure your return the correct help for the prefix requested