message: Update SubNav documentation.
diff: title: SubNav
  ---
  -Use the SubNav component to style navigation with a minimal underlined selected state, typically used for navigation placed at the top of the page.
  +Use the SubNav component for navigation on a dashboard-type interface with another set of navigation components above it. This helps distinguish navigation hierarchy.
  To use SubNav with [react-router](https://github.com/ReactTraining/react-router) or
  [react-router-dom](https://www.npmjs.com/package/react-router-dom), pass
  