title: WTForms RadioField default values
body: <p>I'm generating a html form with wtforms like this:</p>
  
  <pre><code>&lt;div class="control-group"&gt;
      {% for subfield in form.time_offset %}
      &lt;label class="radio"&gt;
          {{ subfield }}
          {{ subfield.label }}
      &lt;/label&gt;
      {% endfor %}
  &lt;/div&gt;
  </code></pre>
  
  <p>My form class is like this:</p>
  
  <pre><code>class SN4639(Form):
      time_offset = RadioField(u'Label', choices=[
          ('2', u'Check when Daylight saving has begun, UTC+02:00'),
          ('1', u'Check when Daylight saving has stopped, UTC+01:00')],
          default=2, validators=[Required()])
  </code></pre>
  
  <p>When I now open the edit form, I get via SQL the value 1 or 2 - how can I preset the specifiy radiobutton?</p>