title: How to know if element is already in the DOM when creating new Backbone view
body: <p>here's the situation: 
  When page is opened for the first time, it already has prepared DOM by server(php). </p>
  
  <p>If user has javascript turned on, then i want to convert my page to web app(or whatever you call it).
  As soon as Javascript is initialized, Backbone fetches collection from server. 
  The problem is, that some of these fetched items are already on page. </p>
  
  <p>Now how can i mark those items which already are in the DOM?
  And how can i tie them up with the Backbone view?</p>