title: Youtube iframe "loop" doesn't work
body: <p>I tried to use the <a href="https://developers.google.com/youtube/youtube_player_demo?hl=zh-tw" rel="noreferrer">YouTube player demo</a> to generate the code necessary for my video to autoplay and loop itself.
  But only the autoplay works, it doesn't loop, and the demo-video doesn't work either. Here is the code I've used.</p>
  
  <pre><code>&lt;iframe class="embed-responsive-item" id="ytplayer" type="text/html" width="640" height="360" src="https://www.youtube.com/embed/M7lc1UVf-VE?&amp;autoplay=1&amp;loop=1&amp;rel=0&amp;showinfo=0&amp;color=white&amp;iv_load_policy=3" frameborder="0" allowfullscreen&gt;
  &lt;/iframe&gt;
  </code></pre>