Tweak the configuration

<table>
  <tr>
    <th>Q</th><th>A</th>
  </tr>
  <tr>
    <td>Bug fix?</td><td>no</td>
  </tr>
  <tr>
    <td>New feature?</td><td>no</td>
  </tr>
  <tr>
    <td>BC breaks?</td><td>no</td>
  </tr>
  <tr>
    <td>Tests pass?</td><td>not yet</td>
  </tr>
  <tr>
    <td>License?</td><td>MIT</td>
  </tr>
</table>

Use BooleanNode for xhtml and strict on filter_sets configuration.

It is an addition to #40