def run
      raise Error, 'message required' unless message
      self.class.switches.each do |switch|
        if send(:"#{switch}?")
          args << "--#{switch}"
          args << send(switch).to_s if send(switch) && !(TrueClass === send(switch))
        end
      end
      Growl.exec *args
    end
def run
      raise Error, 'message required' unless message
      self.class.switches.each do |switch|
        if send(:"#{switch}?")
          args << "--#{switch}"
          args << send(switch).to_s if send(switch) && !(TrueClass === send(switch))
        end
      end
      Growl.exec *args
    end
Initialize with optional +block+, which is then
 instance evaled or yielded depending on the blocks arity.

 Run the notification, only --message is required.