Add gif file aligned on top of README

Closes js-cookiegh-180.

Author: FagnerMartinsBrack

README.md

@@ -1,3 +1,7 @@
+<p align="center">
+  <img src="https://cloud.githubusercontent.com/assets/835857/14581711/ba623018-0436-11e6-8fce-d2ccd4d379c9.gif">
+</p>
+
 # JavaScript Cookie [![Build Status](https://travis-ci.org/js-cookie/js-cookie.svg?branch=master)](https://travis-ci.org/js-cookie/js-cookie) [![Code Climate](https://codeclimate.com/github/js-cookie/js-cookie.svg)](https://codeclimate.com/github/js-cookie/js-cookie)
 
 A simple, lightweight JavaScript API for handling cookies