title: Change markercluster depending quantity
body: <p>I was reading this thread: <a href="https://stackoverflow.com/questions/4416089/google-maps-api-v3-custom-cluster-icon">Google Maps Api v3, custom Cluster icon</a></p>
  
  <p>The thread, explain how we can change the icons of our makrerclusters but, is possible add as variable the quantity? I mean, if the group is of 2 markers display x image, if the group is of 6  markers display other image, etc.</p>