[README] Added a table of contents and some small rewording

The table of contents should make it easier to browse the README.

README.md

@@ -2,6 +2,15 @@
 
 React Native enables you to build world-class application experiences on native platforms using a consistent developer experience based on JavaScript and [React](http://facebook.github.io/react). The focus of React Native is on developer efficiency across all the platforms you care about - learn once, write anywhere. Facebook uses React Native in multiple production apps and will continue investing in React Native.
 
+- [Getting Started](#getting-started)
+- [Getting Help](#getting-help)
+- [Documentation](#documentation)
+- [Examples](#examples)
+- [Extending React Native](#extending-react-native)
+- [Opening Issues](#opening-issues)
+- [Contributing](#contributing)
+- [License](#license)
+
 ## Getting Started
 
 - Follow the [Getting Started guide](http://facebook.github.io/react-native/docs/getting-started.html) to install React Native and its dependencies.
@@ -20,13 +29,13 @@ React Native enables you to build world-class application experiences on native
 
 ## Documentation
 
-- [The website’s documentation](https://facebook.github.io/react-native/docs/) divided into multiple sections.
-There are **Guides** that discuss topics like [debugging](https://facebook.github.io/react-native/docs/debugging.html), [integrating with existing apps](https://facebook.github.io/react-native/docs/embedded-app-ios.html), and [the gesture responder system](https://facebook.github.io/react-native/docs/gesture-responder-system.html).
+[The website’s documentation](https://facebook.github.io/react-native/docs/) divided into multiple sections.
+- There are **Guides** that discuss topics like [debugging](https://facebook.github.io/react-native/docs/debugging.html), [integrating with existing apps](https://facebook.github.io/react-native/docs/embedded-app-ios.html), and [the gesture responder system](https://facebook.github.io/react-native/docs/gesture-responder-system.html).
 - The **Components** section covers React components such as [`View`](https://facebook.github.io/react-native/docs/view.html) and [`Navigator`](https://facebook.github.io/react-native/docs/navigator.html).
 - The **APIs** section covers other libraries like [Animated](https://facebook.github.io/react-native/docs/animated.html) and [StyleSheet](https://facebook.github.io/react-native/docs/stylesheet.html) that aren’t React components themselves.
 - Finally, React Native provides a small number of **Polyfills** that offer web-like APIs.
 
-Another great way to learn more about the components and APIs included with React Native is to read their source. Look under the `Libraries` directory for components like `ScrollView` and `Navigator`, for example. The UIExplorer example is also here to demonstrate some of the ways to use these components. By looking at the source you can get an accurate understanding of each component’s behavior and API.
+Another great way to learn more about the components and APIs included with React Native is to read their source. Look under the `Libraries` directory for components like `ScrollView` and `Navigator`, for example. The UIExplorer example is also here to demonstrate some of the ways to use these components. From the source you can get an accurate understanding of each component’s behavior and API.
 
 The React Native documentation only discusses the components, APIs and topics specific to React Native (React on iOS and Android). For further documentation on the React API that is shared between React Native and React DOM, refer to the [React documentation](http://facebook.github.io/react/).