title: React Navigation : Back button doesn't go to previous scene but to initialRouteName
body: <p>I'm using react-native 0.50.3 with the react-navigation package. I've some issues to go to previous scene using the back button of the phone. Is it related to the last version of RN ?</p>
  
  <p>This is the used code : </p>
  
  <p>App.js defining drawer and stacknavigator : </p>
  
  <pre><code>import React from "react";
  import {TabView, TabBarBottom} from 'react-navigation';
  import { Platform } from "react-native";
  
  import { Root } from "native-base";
  import { StackNavigator, TabNavigator, DrawerNavigator  } from "react-navigation";
  
  
  import SideBar from "./main_scenes/sidebar/";
  import HomeServices from "./main_scenes/services/";
  import Profile from "./main_scenes/profile/";
  
  
  import Splashscreen from "./main_scenes/home/splash";
  import Services from "./main_scenes/services/servicesdetails/";
  
  const Drawer = DrawerNavigator(
    {
  
      Splashscreen:{screen:Splashscreen},
      Services:{screen:Services},
  
    },
    {
      initialRouteName: "Splashscreen",
      contentOptions: {
        activeTintColor: "#e91e63"
      },
      contentComponent: props =&gt; &lt;SideBar {...props} /&gt;
    }
  );
  
  const Feedstack = StackNavigator(
      {
          Drawer: { screen: Drawer },
          HomeServices:{screen:HomeServices},
          Profile:{screen:Profile},
      },
      {
          initialRouteName: "Drawer",
          headerMode: "none",
      }
  );
  
  export default () =&gt;
    &lt;Root&gt;
      &lt;Feedstack /&gt;
    &lt;/Root&gt;;
  </code></pre>
  
  <p>And this how i navigate from a scene to other : </p>
  
  <p>From my scene called "services" to "servicesdetails". First, i've a array for all my data within the route as a variable </p>
  
  <pre><code>    const datas = [
        {
          img: img1,
          text: "Some text,
          note: "Its time to build a difference . .",
          route: "Services",
        },
   {
      img: img2,
      text: "Some text",
      note: "Its time to build a difference . .",
      route : "Another_one_for_test"
    },
      ]
  </code></pre>
  
  <p>Then in the render(), i use : </p>
  
  <pre><code> &lt;Content&gt;
            &lt;List
              dataArray={datas}
              renderRow={data =&gt;
                &lt;ListItem button thumbnail onPress={() =&gt; this.props.navigation.navigate(data.route)}&gt;
                  &lt;Left&gt;
                    &lt;Thumbnail square size={80} source={data.img} /&gt;
                  &lt;/Left&gt;
                  &lt;Body&gt;
                    &lt;Text &gt;{data.text}&lt;/Text&gt;
                    &lt;Text numberOfLines={1} note&gt;{data.note}&lt;/Text&gt;
                  &lt;/Body&gt;
  
                &lt;/ListItem&gt;}
            /&gt;
          &lt;/Content&gt;
  </code></pre>
  
  <p>My navigation goes very well, but from the scene details to the services's scene, cannot be back neither from the previous button, nor from the back button of the phone.</p>
  
  <p>the function <code>&lt;Button transparent onPress={() =&gt; this.props.navigation.goBack()}&gt;</code> send me directly to "splashscreen" defined as the initialroutename in the app.js. Same for the back button.</p>
  
  <p>Is there something i've done wrong ?</p>
  
  <p>Thanks</p>