title: Ember-data hasMany association not working
body: <p>I have a couple models set up like follows:</p>
  
  <pre><code>WT.WorkoutPlan = DS.Model.extend({
     workouts: DS.hasMany('planWorkout'),
     name: DS.attr()
  });
  
  WT.PlanWorkout = DS.Model.extend({});
  </code></pre>
  
  <p>When I attempt to load the model with the following JSON, the workout is loaded fine as evidenced by <code>plan.get('name');</code> returning the name correction, but <code>plan.get('workouts')</code> always has 0 members.  Anyone know why the association isn't loading?</p>
  
  <p>Here's the JSON:</p>
  
  <pre><code>{
       "planWorkouts": [
           {
              "id": 991,
              "name": "Lower Body"
           }
       ],
       "workoutPlan": {
           "id": 343,
           "name": "male-20to39-fat-loss",
           "planWorkouts": [991]
       }
  }
  </code></pre>
  
  <p>I'm using ember-data 1.0beta3</p>