text: import { createAppContainer} from 'react-navigation'
  import { createStackNavigator} from 'react-navigation'
  
  import PeoplePage from './src/screens/PeoplePage'
  import PersonDetail from './src/screens/PersonDetail'
  import capitalizeFirstLetter from './src/util/capitalizeFirstLetter'
  
  const StackNavigator = createStackNavigator({
    'Main':{
      screen: PeoplePage
    },
    'PersonDetail':{
      screen: PersonDetail,
      navigationOptions: ({navigation}) => {
        const personName = navigation.state.params.person.name.first
  
        return({
          title: capitalizeFirstLetter(personName),
          headerTitleStyle: {
            color: 'white',
            fontSize: 30
          }
        })
      }
    }  
    }, {
      defaultNavigationOptions: {
        title: 'Contatos',
        headerTitleStyle: {
          color: 'white',
          fontSize: 30,
          flexGrow: 1,
          textAlign: 'center'
        },
        headerStyle: {
          backgroundColor: '#c6a2f7',
          borderBottomWidth: 1,
          borderBottomColor: '#C5C5C5'
        }
      }
    }
  )
  
  const AppContainer = createAppContainer(StackNavigator)
  
  export default AppContainer