message: Updated nav react native readme to component api
diff: ```jsx
  import { StateNavigator } from 'navigation';
  import { NavigationHandler, NavigationContext } from 'navigation-react';
  -import { NavigationStack } from 'navigation-react-native';
  +import { NavigationStack,. Scene } from 'navigation-react-native';
  const stateNavigator = new StateNavigator([
  { key: 'hello' },
  @@ -13,12 +13,11 @@ const stateNavigator = new StateNavigator([
  const Hello = () => {
  const { stateNavigator } = useContext(NavigationContext);
  return (
  - <TouchableHighlight
  + <Button
  + title="Hello"
  onPress={() => {
  stateNavigator.navigate('world', { size: 20 });
  - }}>
  - <Text>Hello</Text>
  - </TouchableHighlight>
  + }} />
  );
  };
  @@ -27,18 +26,12 @@ const World = () => {
  return <Text style={{ fontSize: data.size }}>World</Text>;
  };
  -const { hello, world } = stateNavigator.states;
  -
  -hello.renderScene = () => <Hello />;
  -world.renderScene = () => <World />;
  -
  -stateNavigator.navigate('hello');
  -
  const App = () => (
  <NavigationHandler stateNavigator={stateNavigator}>
  - <NavigationStack />
  + <NavigationStack>
  + <Scene stateKey="hello"><Hello /></Scene>
  + <Scene stateKey="world"><World /></Scene>
  + </NavigationStack>
  </NavigationHandler>
  );
  -
  -export default App;
  ```
  \ No newline at end of file
  