code: function numbers(arr, i) {
    var values = filterType(arr, 'number');
    return i ? values[i] : values;
  }
docs: Filter `array`, returning only the numbers.
  
  ```js
  var arr = ['a', {a: 'b'}, 1, 'b', 2, {c: 'd'}, 'c'];
  
  utils.numbers(arr);
  //=> [1, 2]
  ```
  
  @param  {Array} `array`
  @param  {Array} `index` Optionally specify the index of the number to return, otherwise all numbers are returned.
  @return {Array} Array of numbers or empty array.
  @api public