Add README latest npm version

[furkanyilmazx]

Use following lines:
[![npm version](https://badge.fury.io/js/office-ui-fabric-react.svg)](https://badge.fury.io/js/office-ui-fabric-react) [![Build Status](https://travis-ci.org/OfficeDev/office-ui-fabric-react.svg?branch=master)](https://travis-ci.org/OfficeDev/office-ui-fabric-react)
And output like that below: