title: React-navigation, tintColor is missing in props validation
body: <p>I have put my react-navigation code into a separate Routes file which I am then importing into my App.js file. Everything is working fine but I am using Airbnb ESLint config in Atom/Nuclide and getting an error with tintColor...</p>
  
  <p><strong>"tintColor is missing in props validation"</strong></p>
  
  <p>Tried this:</p>
  
  <p>Routes.propTypes = { tintColor: PropTypes.string.isRequired,}</p>
  
  <p><strong>But then get error "tintColor PropType is defined but prop is never used"</strong></p>
  
  <p>This is part of the code  </p>
  
  <pre><code>const Routes = () = {
  const ContentNavigator = TabNavigator(
  {
    Profile: { screen: ProfileStack },
    History: { screen: HistoryStack },
    Questions: {
      screen: QuestionsStack,
      navigationOptions: {
        tabBarIcon: ({ tintColor }) =&gt; (
          &lt;Icon name="question-circle" type="font-awesome" size={20} color=
   {tintColor} /&gt;
        ),
      },
    },
    Notifications: { screen: NotificationsStack },
  },
  {
    initialRouteName: 'Profile',
    swipeEnabled: true,
    tabBarOptions: {
      activeTintColor: COLOR_PRIMARY,
    },
    backBehavior: 'none',
  });
  </code></pre>