Add README instructions

A <Video> component for react-native, as seen in

[react-native-login](https://github.com/brentvatne/react-native-login).

### Add it to your project

1. Run `npm install react-native-video --save`

2. Open your project in XCode, right click on `Libraries` and click `Add

   Files to "Your Project Name" [(Screenshot)](http://url.brentvatne.ca/g9Wp).

3. Add `libRTCVideo.a` to `Build Phases -> Link Binary With Libraries`

   [(Screenshot)](http://url.brentvatne.ca/g9Wp).

4. Click on `RCTVideo.xcodeproj` in `Libraries` and go the `Build

   Phases` tab. Double click the text to the right of `Header Search

   Paths` and add `$(SRCROOT)../react-native/React` so XCode is able to

   find the headers that the `RCTVideo` source files are referring to,

   by pointing to the header files installed within the `react-native`

   `node_modules` directory. [(Screenshot)](http://url.brentvatne.ca/7wE0).

5. Whenever you want to use it within React code now you can: `var Video =

   require('react-native-video');`

## Example

```javascript

// Within your render function, assuming you have a file called

// "background.mp4" in your project

<Video source={"background"} style={styles.backgroundVideo} />

// Later on in your styles..

var styles = Stylesheet.create({

  backgroundVideo: {

    resizeMode: 'cover', // stretch and contain also supported

    position: 'absolute',

    top: 0,

    left: 0,

    bottom: 0,

    right: 0,

  },

});

In action [here](https://github.com/brentvatne/react-native-login/blob/master/index.ios.js).