Merge pull request react-navigation#56 from heygema/source

[Typo Fix] One Word Typo.

Author: brentvatne

docs/hello-react-navigation.md

@@ -6,7 +6,7 @@ sidebar_label: Hello React Navigation
 
 In a web browser, you can link to different pages using an anchor (`<a>`) tag. When the user clicks on a link, the URL is pushed to the browser history stack. When the user presses the back button, the browser pops the item from the top of the history stack, so the active page is now the previously visited page. React Native doesn't have a built-in idea of a global history stack like a web browser does -- this is where React Navigation enters the story.
 
-React Navigation's `StackNavigator` provides a way for your app to transition between screens and manage navigation history. If your app uses only one `StackNavigator` then it is conceptually similar to how a  web browser handles navigation state - your app pushes and pops items from the navigation stack as users interact with the it, and this results in the user seeing different screens. A key difference between how this works in a web browser and in React Navigation is that React Navigation's `StackNavigator` provides the gestures and animations that you would expect on Android and iOS when navigating between routes in the stack.
+React Navigation's `StackNavigator` provides a way for your app to transition between screens and manage navigation history. If your app uses only one `StackNavigator` then it is conceptually similar to how a  web browser handles navigation state - your app pushes and pops items from the navigation stack as users interact with it, and this results in the user seeing different screens. A key difference between how this works in a web browser and in React Navigation is that React Navigation's `StackNavigator` provides the gestures and animations that you would expect on Android and iOS when navigating between routes in the stack.
 
 All we need to get started using React Navigation is a `StackNavigator`.