title: Store/push to an array in a Backbone Model
body: <p>I have this model defaults:</p>
  
  <pre><code>test.Models.ItemModel = Backbone.Model.extend({
  
  defaults: {
      name: 'an item',
      units: []
  },
  </code></pre>
  
  <p>Which I then use the following code to set the Model:</p>
  
  <pre><code> addUnit: function(e){
      if(e.keyCode == 13){
        this.model.set({ 'units' : this.model.get('units').push($('#addUnit').val()) }, 
          {success: function(){
            this.render();
          }}
        );
      }
    },
  </code></pre>
  
  <p>However, it never seems to get added to the Model array, am I doing things right here??</p>