title: Delete firebase data older than 2 hours
body: <p>I would like to delete data that is older than two hours. Currently, on the client-side, I loop through all the data and run a delete on the outdated data. When I do this, the <code>db.on('value')</code> function is invoked every time something is deleted. Also, things will only be deleted when a client connects, and what might happen if two clients connect at once?</p>
  <p>Where can I set up something that deletes old data? I have a timestamp inside each object created by a JavaScript <code>Date.now()</code>.</p>