docs(README): add logo and badges

Author: addyosmani

README.md

@@ -1,3 +1,12 @@
+<p align="center">
+  <img src="https://i.imgur.com/NVRZLHv.png" width="640" height="240" alt="quicklink">
+  <br>
+  <a href="https://www.npmjs.org/package/quicklink"><img src="https://img.shields.io/npm/v/quicklink.svg?style=flat" alt="npm"></a>
+  <a href="https://unpkg.com/quicklink"><img src="https://img.badgesize.io/https://unpkg.com/quicklink/dist/quicklink.js?compression=gzip" alt="gzip size"></a>
+  <a href="https://www.npmjs.com/package/quicklink"><img src="https://img.shields.io/npm/dt/quicklink.svg" alt="downloads" ></a>
+  <a href="https://travis-ci.org/addyosmani/quicklink"><img src="https://travis-ci.org/addyosmani/quicklink.svg?branch=master" alt="travis"></a>
+</p>
+
 # quicklink
 > Faster subsequent page-loads by prefetching in-viewport links during idle time