title: Normalizr - not resulting expected
body: <pre><code>import { normalize, Schema, arrayOf } from 'normalizr';
  
  var ListA = [
      {
          id:1, 
          text: "text1",
          comments : [
              {
                  id: 232,
                  text: "asfasd"
              },
              {
                  id: 333,
                  text: "abcsss"
              }
          ]
      }, 
      {id:2, text:"text2", comments:[]}, 
      {id:3, text:"text3", comments:[]}
      ]
  </code></pre>
  
  <p>I am trying to normalize this simple response. I am not sure what is wrong on what I am doing or I haven't understood normalizr documentation.</p>
  
  <pre><code>const post = new Schema('posts');
  // const comment = new Schema('comments');
  // const collection = new Schema('collections');
  
  // post.define({
  //  comments : comment,
  //  collections : arrayOf(collection)
  // });
  ListA = normalize(ListA, {
      posts: arrayOf(post)
  });
  
  console.log(ListA);
  </code></pre>
  
  <p>This just results same response on "result" object, and entities object is empty. Can someone please help me. First I am trying to normalize just the Post and after then would be comment aswell.. But I haven't been able to cross the first step.</p>