tell reader how to install react-native-cli

[micahstubbs]

it would be cool if the companion blog post would tell the reader how to install the react-native-cli node module in the Step 0: Setup and boilerplate section right before the code block that first uses the react-native command

found the install command buried a bit in the react native docs http://facebook.github.io/react-native/docs/getting-started.html#the-react-native-cli

npm install -g react-native-cli

[Abewkayew]

Great.