title: Loading other data like map tiles in modestmaps.js
body: <p>I have a map that's using modestmaps.js quite nicely so far. However, under my naive implementation around 200kb of data is loaded at each zoom level to be rendered as markers (it's in geoJson, but needs quite a bit of client side processing). That single load represents all of the data for that zoom level but waiting for it to complete  is getting annoying. I'd like to switch to something that loads the data only for the displayed map tiles. </p>
  
  <p>Having the server return the correct data for an <code>{x}/{y}/{z}</code> style request won't be hard but is there a simple way to have modestmaps handle the requesting part client side for me? I'd be hoping for some sort of <code>TemplatedLayer</code> that I could maybe give a url and a callback.</p>
  
  <p>Any suggestions?</p>