def add(job)
      if @workers.empty?
        @work_queue.insert(0, job)
      else
        worker = @workers.pop()
        ask_worker(worker, job)
      end
    end
def add(job)
      if @workers.empty?
        @work_queue.insert(0, job)
      else
        worker = @workers.pop()
        ask_worker(worker, job)
      end
    end
Places a job on the work queue. This method is executed asynchronously.
 @param [Object] job work to be processed