message: adds m + p utils to UnderlineNav
diff: @@ -8,8 +8,7 @@ export const ITEM_CLASS = 'UnderlineNav-item no-underline'
  export const SELECTED_CLASS = 'selected'
  export default function UnderlineNav(props) {
  - const {actions, align, children, full, label, ...rest} = props
  - const {className} = mapWhitespaceProps(rest)
  + const {actions, align, children, full, label, className} = mapWhitespaceProps(props)
  const classes = classnames(className, 'UnderlineNav', align && `UnderlineNav--${align}`, full && 'UnderlineNav--full')
  const mappedChildren = React.Children.map(children, child => {
  