title: how to get Ember-Data RESTAdapter to send "hasMany" records to server
body: <p>I'm using Ember-Data beta 3.  My Ds.models are similar to the following:</p>
  
  <pre><code>App.Item = DS.Model.extend({
    itemName: DS.attr('string'),
    strategy: DS.belongsTo('strat')
  });
  
  App.Strat = DS.Model.extend({
      stratName: DS.attr('string'),
      items: DS.hasMany('item',{async:true})
  });
  </code></pre>
  
  <p>Using Ember-data's RESTAdapter, I'm able to populate the model using data from my server.  But when I tried to persist data back to the server, none of the "App.Item" records got sent.  The JSON received by my server only contained "stratName."  I used "this.get('model').save()" to trigger the send.</p>
  
  <p>What am I doing wrong?</p>