title: Inform ember-data about server changes
body: <p>I am currently planning a complex application using ruby on rails and ember.js. What I have seen about ember-data so far is that it caches records automatically; <code>post.comments</code> will first result in a Ajax-call to fetch all comments for the given post, but if the user visits the same route the next time, it will just fetch the records from the store-cache.</p>
  
  <p>The problem is: What if another user added a comment to this post? How to tell ember it has to reload its cache because something changed? </p>
  
  <p>I already thought about a solution using websockets to tell clients which stuff to reload - but I don't think this is best-practice. And in addition, I can't imagine this isn't a common problem, so I am wondering what other developers are doing to solve this issue.</p>