def quit
      i = 0
      @group.keys.each do |group|
        wait_until_done(group) do
          if i < 30
            sleep 1
            i += 1
            print "."
          else
            break
          end
        end
      end

      @threads.each { |t| t.kill }
      puts " done."
    end
def quit
      i = 0
      @group.keys.each do |group|
        wait_until_done(group) do
          if i < 30
            sleep 1
            i += 1
            print "."
          else
            break
          end
        end
      end

      @threads.each { |t| t.kill }
      puts " done."
    end
Quit - empty the queue and wait for remaining jobs to complete