code: function(arr, start, end) {
      if (isUndefined(start)) return arr;
      if (isUndefined(end))   end = start;
      arr.splice(start, end - start + 1);
      return arr;
    }
docs: *
  @method removeAt(start, [end])
  @returns Array
  @short Removes element at `start`. If [end] is specified, removes the range
  between `start` and [end]. This method will modify the array!
  
  @example
  
  ['a','b','c'].removeAt(0) -> ['b','c']
  [1,2,3,4].removeAt(1, 2)  -> [1, 4]
  
  @param {number} start
  @param {number} [end]
  
  *