title: data-* attributes does not displaying in CKEditor
body: <p>I'm using CKEditor to allow all types of content to store in my database.  Some HTML content has <code>data-*</code> attributes used for storing values.  When I save the HTML content from the CKEditor by fetching the value using <code>$(".ckeditor").val()</code>, it stores the value in database very well.  However when I fetch ckeditor data from the database and set the value in CKEditor it does not show the <code>data-*</code> attributes in neither source mode nor HTML mode. Nevertheless in the database, I can see the <code>data-*</code> attributes.</p>
  
  <p>I'm using <code>CKEditor 4.5.1</code> version.</p>
  
  <p>In my config file I have set:</p>
  
  <pre><code>config.allowedContent = true;
  config.removeFormatAttributes = '';
  </code></pre>
  
  <p>Can anyone help me on this issues, I have looked into many solutions and it should be working.</p>