title: Is there an Android Material Design onboarding/tutorial overlay/showcase library?
body: <p>I've seen this in Google Calendar. It looks cool:</p>
  
  <p><img src="https://i.stack.imgur.com/3YhJAl.png" alt="enter image description here"></p>
  
  <p>I know about the old <a href="https://github.com/amlcurran/ShowcaseView" rel="noreferrer">ShowCaseView</a> and have seen <a href="https://github.com/stephanenicolas/RoboDemo" rel="noreferrer">RoboDemo</a> but neither seem to be updated for Material Design.</p>
  
  <p>Is there a library that means we don't have to roll/adapt our own?</p>