Synopsis:
   topic <channel> [<new topic>]
   topic [<new topic>]
   
Description:
   With this command you can change the current topic of the specified
   channel.  If no new topic is specified, the current one is displayed.
   If the new topic is not specified AND either the channel name is prefixed
   with a hyphen (a "-") or the hyphen is the only argument, the topic
   for the assumed channel will be removed.

Examples:
   To set a new topic on your channel:
      /topic blah Welcome to blah, a very serious channel.
      or
      /topic Welcome to blah, a very serious channel.

   To view the current topic for your channel:
      /topic blah
      or
      /topic
      
   To unset the topic for your channel:
      /topic -blah
      or
      /topic -