title: Android new Bottom Navigation bar or BottomNavigationView
body: <p>Saw the new guideline came out, and used in <code>google photos</code> latest app.
  Have no idea how to use the new Bottom Navigation Bar.
  See through the new support lib, didn't find any lead.</p>
  
  <p><img src="https://i.stack.imgur.com/6lcXBm.png" alt="enter image description here"></p>
  
  <p>Can not find any official sample.</p>
  
  <p>How to use the new Bottom bar? Don't want to do any customize.</p>