message: Shared navigate back function
diff: @@ -4,10 +4,7 @@ import {NavigationBackAndroid} from 'navigation-react-native';
  export default ({color, colorRef, moveScene, stateNavigator}) => {
  const {url} = stateNavigator.stateContext;
  - return (
  - <View style={styles.detail}>
  - <NavigationBackAndroid
  - navigating={() => {
  + const navigateBack = () => {
  colorRef.measure((ox, oy, w, h, x, y) => {
  if (url === stateNavigator.stateContext.url) {
  stateNavigator.navigateBack(1);
  @@ -15,18 +12,15 @@ export default ({color, colorRef, moveScene, stateNavigator}) => {
  }
  });
  return false;
  - }}
  + };
  + return (
  + <View style={styles.detail}>
  + <NavigationBackAndroid
  + navigating={navigateBack}
  stateNavigator={stateNavigator} />
  <TouchableHighlight
  underlayColor="#fff"
  - onPress={() => {
  - colorRef.measure((ox, oy, w, h, x, y) => {
  - if (url === stateNavigator.stateContext.url) {
  - stateNavigator.navigateBack(1);
  - moveScene({w, h, x, y});
  - }
  - });
  - }}>
  + onPress={navigateBack}>
  <Text style={styles.back}>X</Text>
  </TouchableHighlight>
  <View
  