title: how to check sidekiq status without an extension
body: <p>On the sidekiq wiki it says I can check the status of sidekiq by polling it.
  I know when I perform delay method sidekiq will return the process id, but how do check Sidekiq to see if the id is finished processing.</p>
  
  <p>I would expect some code like this:</p>
  
  <pre><code>if Sidekiq.check_complete?(process_id)
      puts 'Process completed'
  end
  </code></pre>
  
  <p>I want to do this without any extra gems.</p>