title: Check if a resque job with specific args is pending in queue
body: <p>For example I enqueued a job as so </p>
  
  <pre class="lang-ruby prettyprint-override"><code>Resque.enqueue(MyJob, user.id)
  </code></pre>
  
  <p>Before en-queueing another job with the same <code>user.id</code> I would like to check if there already exists a job with that user id in the queue.</p>
  
  <p>I hope there is some syntax like:</p>
  
  <pre class="lang-ruby prettyprint-override"><code>Resque.queue('MyQueue').has_pending_job(MyJob, user.id)
  </code></pre>