code: function makePercent(formatter) {
    return function percentWrapped(value) {
      if (value != null) {
        return formatter(value * 100) + '%';
      }
  
      return formatter(value);
    };
  }
docs: Wraps a formatting function by multiplying the value by 100 and
  adds a % to the end.
  
  @param {Function} formatter formatter function
  @return {Function} a formatter function