title: Wordpress API settings not savnig
body: <p>I have a pretty simple settings page for my plugin. here is the code: <a href="http://pastebin.com/k5jeZ9aw" rel="nofollow">http://pastebin.com/k5jeZ9aw</a></p>
  
  <p>It has just one text field and shows fine. However it does not save. Actually, when it gets to method 'validate_setting' it gets a void parameter (I assume it should get the value of the field).</p>
  
  <p>I don't get neither any js errors nor wordpress debug errors.</p>
  
  <p>I don't know if the problem is due to the fact of being using a class, but it does not complain about not finding any function.</p>
  
  <p>Please anybody could help me?</p>
  
  <p>Thanks in advance.</p>