title: notifyItemInserted in runOnUiThread not work
body: <p>For me, <code>notifyItemInserted</code> in <code>runOnUiThread</code> does not work.
  I have <code>runOnUiThread</code> in <code>asyncTask</code> after download each file:</p>
  
  <pre><code>  ImageModel imageModel = new ImageModel();
    imageModel.setName("تصویر " );
    imageModel.setUrl(aFile.getName());
    imageModel.ImageFile = localFile;
    data.add(imageModel);
    runOnUiThread(new Runnable() {
         @Override
         public void run() {
              mAdapter.notifyItemInserted(data.size() - 1);
         }
    });
  </code></pre>