title: Get selected button's value from Polymer radio group with jquery
body: <p>I want to get the value from a polymer 1.0 radio group and save it to a database:</p>
  
  <p><strong>HTML:</strong></p>
  
  <pre><code>&lt;paper-radio-group selected="small"&gt;
    &lt;paper-radio-button name="small"&gt;Small&lt;/paper-radio-button&gt;
    &lt;paper-radio-button name="medium"&gt;Medium&lt;/paper-radio-button&gt;
    &lt;paper-radio-button name="large"&gt;Large&lt;/paper-radio-button&gt;
  &lt;/paper-radio-group&gt;
  </code></pre>
  
  <p><strong>Script:</strong></p>
  
  <pre><code>var size = $('input[selected]:checked').val();
  </code></pre>
  
  <p>Is there a simple way with jQuery? Do I need to add an id on paper-radio-group?</p>