title: Openlayers 3 security issue
body: <p>I have an issue with Openlayers 3.
  When I want to load mapbox tiles like this :</p>
  
  <pre><code>source:new ol.source.TileJson({
  url: 'http://api.tiles.mapbox.com/v3/mapbox.world-dark.jsonp'
  })
  </code></pre>
  
  <p>I have this message :</p>
  
  <p>SecurityError: The operation is insecure.</p>
  
  <p>Could you help me ?</p>
  
  <p>Thanks !</p>