title: How are attributes parsed in Boost.PropertyTree?
body: <p>Say I have this XML format:  </p>
  
  <pre><code>&lt;Widget type="SomeWidget" name="foo"&gt;
     &lt;Event name="onmouseover"&gt;
        dostuff();
     &lt;/Event&gt;
  &lt;/Widget&gt;
  </code></pre>
  
  <p>How do I read the attributes using Boost.PropertyTree?</p>