title: summernote textarea with attribute required does not work
body: <p>I am using the WYSIWYG Editor <a href="http://summernote.org/" rel="nofollow noreferrer">summernote</a>.</p>
  
  <p>I have a textarea</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;textarea name="data[Text][text]" rows="3" class="form-control" autofocus="autofocus" cols="30" id="TextText" required="required"&gt;&lt;/textarea&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>and a javascript: </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$(document).ready(function() {
    $('#TextText').summernote({
      height: 250,
      toolbar: [
        ['style', ['bold', 'italic', 'underline', ]],
        ['para', ['ul', 'ol', 'paragraph']],
      ]
    });
  });</code></pre>
  </div>
  </div>
  </p>
  
  <p>As you can see the the textarea has the attribute required, but after I apply the summernote to the textarea, submitting an empty form throws a javascript message in chrome : </p>
  
  <blockquote>
    <p>An invalid form control with name='data[Text][text]' is not focusable.</p>
  </blockquote>
  
  <p>Firefox does not throw any error but also doesn't indicate that the input is required.</p>
  
  <p>How can I force summernote to keep the required attribute?</p>