title: Automatically strip() all values in WTForms?
body: <p>Is there any way to strip surrounding whitespace from all values in WTForms without adding a filter to every single field?</p>
  
  <p>Currently I'm passing <code>filters=[strip_whitespace]</code> with the function shown below to my fields but having to repeat this for every field is quite ugly.</p>
  
  <pre><code>def strip_whitespace(s):
      if isinstance(s, basestring):
          s = s.strip()
      return s
  </code></pre>
  
  <p>A solution requiring subclassing of <code>Form</code> would be fine since I'm already doing that in my application.</p>