title: ThemeData - deprecated title argument
body: <p>I tried to find an answer for the question "how to correctly code the depreciated 'title' argument of ThemeData?" (I am following a tutorial). However I found the correct answer bewteen some comments in other topic. I leave the answer below for future references and an easy finding. </p>
  
  <pre><code>theme: new ThemeData(
    primaryTextTheme: TextTheme(
        title: TextStyle(
  color: Colors.white,
  ))),
  </code></pre>
  
  <p><a href="https://stackoverflow.com/questions/50619848/how-to-change-text-color-of-appbar-icon-color-of-fab-universally-using-theme/53463604">How to change text color of AppBar, icon color of FAB universally using theme?</a></p>
  
  <p>Answer by eMarine: <a href="https://stackoverflow.com/users/1584407/emarine">https://stackoverflow.com/users/1584407/emarine</a></p>