title: Iterate through DS.hasMany
body: <p>In my application I have <code>Course</code> and <code>TeamMember</code> models, so that each team member can be responsible for several courses:</p>
  
  <pre><code>FrontApp.TeamMember = DS.Model.extend({
    name:    DS.attr('string'),
    email:   DS.attr('string'),
    image:   DS.attr('string'),
    courses: DS.hasMany('course', {async: true})
  });
  
  FrontApp.Course = DS.Model.extend({
    title:       DS.attr('string'),
    ...
    bunch of other model-specific fields (no relations)
    ...
    ects:        DS.attr('number')
  });
  </code></pre>
  
  <p>Now I want to display the following on profile page:</p>
  
  <ul>
  <li><code>is responsible for COURSE_TITLE_1, COURSE_TITLE_2</code> if he is responsible for &lt;= 2 courses</li>
  <li><code>is responsible for COURSE_TITLE_1, COURSE_TITLE_2, ...</code> if he is responsible for > 2 courses</li>
  </ul>
  
  <p>Currently I am trying to do that from itemController:</p>
  
  <pre><code>FrontApp.TeamMemberController = Ember.ObjectController.extend({
    responsibleForCourses: function(){
      var res = "";
  
      this.get('courses').then(function(loaded_courses){
          if ( loaded_courses.get('length') &lt;= 2 ) {
              loaded_courses.forEach(function(course){
                  res += course.get('title') + " | ";
              })
          } else {
              // access first two of loaded_courses here and add "..."
          } 
          console.log(res); // this thing works
      })
  
      return res; // but here it does not work
    }.property('courses')
  });
  </code></pre>
  
  <p>Since the <code>model.courses</code> is a promise, I had to use <code>.then()</code>, but this caused the following problem: how do I return my <code>res</code> and display it in my template?</p>
  
  <p>Btw, my template looks like this: </p>
  
  <pre><code>responsible for courses: {{responsibleForCourses}}
  </code></pre>
  
  <p>Thanks in advance for your help.</p>