code: function(start, len) {
          if ('number' === typeof start) {
  
            if ((start < 0) || (start >= get(this, 'length'))) {
              throw new EmberError(OUT_OF_RANGE_EXCEPTION);
            }
  
            // fast case
            if (len === undefined) len = 1;
            this.replace(start, len, EMPTY);
          }
  
          return this;
        }
docs: Remove an object at the specified index using the `replace()` primitive
  method. You can pass either a single index, or a start and a length.
  
  If you pass a start and length that is beyond the
  length this method will throw an `OUT_OF_RANGE_EXCEPTION`.
  
  ```javascript
  var colors = ["red", "green", "blue", "yellow", "orange"];
  colors.removeAt(0);     // ["green", "blue", "yellow", "orange"]
  colors.removeAt(2, 2);  // ["green", "blue"]
  colors.removeAt(4, 2);  // Error: Index out of range
  ```
  
  @method removeAt
  @param {Number} start index, start of range
  @param {Number} len length of passing range
  @return {Ember.Array} receiver