title: Sort Issues Returned by GitLab API by Update Timestamp
body: <p>When I do the following requests on my GitLab instance they return identical output:</p>
  
  <pre><code>curl -o updated.json https://gitlab.domain.com/api/v3/projects/37/issues?private_token=${GITLAB_TOKEN}&amp;order_by=updated_at
  curl -o created.json https://gitlab.domain.com/api/v3/projects/37/issues?private_token=${GITLAB_TOKEN}
  </code></pre>
  
  <p>I would expect the <code>updated.json</code> to be ordered by the <code>updated_at</code> field in the issue, however they are still ordered by <code>created_at</code>.</p>
  
  <p>Am I missing something obvious? The source code has the <a href="https://github.com/gitlabhq/gitlabhq/blob/8-1-stable/lib/api/issues.rb#L81" rel="nofollow"><code>issues.reorder(issuable_order_by =&gt; issuable_sort)</code></a> in it so I would expect them to be correctly sorted?</p>