update string manipulation to use URI.js

app/assets/javascripts/clusters.js.coffee

@@ -5,9 +5,7 @@
 # Change the src of the given image with an updated timestamp to get the latest version
 # @param node - DOM image tag object of the Ganglia image to update
 startRefresh = (node) ->
-  if node.src.indexOf('timestamp=') > -1
-    node.src = node.src.split('timestamp=')[0] + 'timestamp=' + (new Date).getTime()
-  return
+  node.src = URL(node.src).setQuery("timestamp", (new Date).getTime()).toString()
 
 # anonymous function to update all visible Ganglia graphs every 5 seconds
 (refreshImages = ->