Add shields to README

Author: wojtekmaj

README.md

@@ -1,3 +1,7 @@
+![downloads](https://img.shields.io/npm/dt/react-clock.svg) ![build](https://img.shields.io/travis/wojtekmaj/react-clock.svg) ![dependencies](https://img.shields.io/david/wojtekmaj/react-clock.svg
+) ![dev dependencies](https://img.shields.io/david/dev/wojtekmaj/react-clock.svg
+) [![tested with jest](https://img.shields.io/badge/tested_with-jest-99424f.svg)](https://github.com/facebook/jest)
+
 # React-Clock
 
 A component to display clock for your React application.