code: function(obj) {
          // fail fast
          if (!Enumerable.detect(obj)) return false;
  
          var loc = get(this, 'length');
          if (get(obj, 'length') !== loc) return false;
  
          while(--loc >= 0) {
            if (!obj.contains(this[loc])) return false;
          }
  
          return true;
        }
docs: Returns true if the passed object is also an enumerable that contains the
  same objects as the receiver.
  
  ```javascript
  var colors = ["red", "green", "blue"],
  same_colors = new Ember.Set(colors);
  
  same_colors.isEqual(colors);               // true
  same_colors.isEqual(["purple", "brown"]);  // false
  ```
  
  @method isEqual
  @param {Ember.Set} obj the other object.
  @return {Boolean}