title: OpenLayers Cluster Recalculate
body: <p>So, I have a number of items clustered in OpenLayers.</p>
  
  <p>I'm using a strategy that clusters the items based on their attributes.</p>
  
  <p>I change an item's attribute.</p>
  
  <p>How do I get the clustering strategy to recalculate the cluster?</p>