Revert "Feature Hand Back Key for Android" (#835)

src/Reducer.js

@@ -22,7 +22,6 @@ import {
 
 import { assert } from './Util';
 import { getInitialState } from './State';
-import { Platform } from 'react-native';
 
 // WARN: it is not working correct. rewrite it.
 function checkPropertiesEqual(action, lastAction) {
@@ -73,11 +72,6 @@ function inject(state, action, props, scenes) {
     case POP_ACTION2:
     case POP_ACTION: {
       assert(!state.tabs, 'pop() operation cannot be run on tab bar (tabs=true)');
-
-      if (Platform.OS === 'android') {
-        assert(state.index > 0, 'You are already in the root scene.');
-      }
-
       if (state.index === 0) {
         return state;
       }

src/Router.js

@@ -10,7 +10,6 @@ import React, {
   Component,
   PropTypes,
 } from 'react';
-import { BackAndroid } from 'react-native';
 import NavigationExperimental from 'react-native-experimental-navigation';
 
 import Actions from './Actions';
@@ -99,15 +98,6 @@ class Router extends Component {
   render() {
     if (!this.state.reducer) return null;
 
-    BackAndroid.addEventListener('hardwareBackPress', () => {
-      try {
-        Actions.pop();
-        return true;
-      } catch (err) {
-        return false;
-      }
-    });
-
     return (
       <NavigationRootContainer
         reducer={this.state.reducer}