title: get() is returning arrays as non-arrays
body: <p>I have this model:</p>
  
  <pre><code>let model = new falcor.Model({
      cache: {
          hStudents: {
              801: {
                  FirstName: 'Samuel',
                  LastName: 'Forbes'
                  },
              802: {
                  FirstName: 'Chad',
                  LastName: 'Pennington'
                  }
              },
          lStudents: [
              $ref(['hStudents', 801]),
              $ref(['hStudents', 802])
              ]
          }
      });
  </code></pre>
  
  <p>When I execute the following code, although lStudents is an array in the model, I'm getting back an object which is not an array. For that reason, I cannot use Angular's *ngFor to iterate over the object. Why would I not get an array back?</p>
  
  <pre><code>return this.model.get("lStudents[0..1]['FirstName','LastName']")
      .progressively()
      .subscribe( (h) =&gt; {
          console.log(JSON.stringify(h));
          });
  </code></pre>
  
  <p>prints:</p>
  
  <pre><code>{"json":{
    "lStudents":{
      "0":{"$__path":["hStudents","801"],"FirstName":"Samuel","LastName":"Forbes"},
      "1":{"$__path":["hStudents","802"],"FirstName":"Chad","LastName":"Pennington"},"$__path":["lStudents"]}
    }
  }
  </code></pre>