title: Marker clusterer calls zoom_changed event of the map twice
body: <p>I'm using this third party library, called Marker Clusterer with the Google Maps API. <a href="http://google-maps-utility-library-v3.googlecode.com/svn/trunk/markerclustererplus/docs/reference.html" rel="nofollow">http://google-maps-utility-library-v3.googlecode.com/svn/trunk/markerclustererplus/docs/reference.html</a></p>
  
  <p>I am trying to trigger an event when the map's zoom level is changed. The odd thing I've noticed though, is that when you click on a marker cluster, it calls the zoom event twice. Has anyone come across this odd error before? Why would it trigger the zoom callback twice? When I zoom normally without using clusters, the zoom callback is only called once. </p>
  
  <p>Any ideas?</p>