message: Added navigation back for android gesture sample
diff: import React from 'react';
  import {Dimensions, StyleSheet, Text, View, TouchableHighlight, PanResponder} from 'react-native';
  -import {spring} from 'navigation-react-native';
  +import {NavigationBackAndroid, spring} from 'navigation-react-native';
  export default class Next extends React.Component {
  constructor(props) {
  @@ -38,6 +38,7 @@ export default class Next extends React.Component {
  ]}
  {...this.panResponder.panHandlers}
  >
  + <NavigationBackAndroid stateNavigator={stateNavigator} />
  <TouchableHighlight
  underlayColor="transparent"
  onPress={() => {
  