Add screenshot to readme

Author: javierbyte

README.md

@@ -4,6 +4,8 @@ This is a tool that can convert any image into a pure css image.
 
 [Live demo](http://javier.xyz/img2css/)
 
+[![img2css](screenshot.png)](http://javier.xyz/img2css/)
+
 ## How this works?
 
 Well, it just puts the image in a canvas, calculates an array with the rgb values, and then... just creates a single pixel shadow for every value!

index.html

@@ -10,7 +10,7 @@
 
     <script src="static/bundle.js"></script>
 
-    <a target='_blank' style="position: fixed; top: 0; right: 0" href="https://github.com/javierbyte/img2css"><img style="position: absolute; top: 0; left: 0; border: 0;" src="https://camo.githubusercontent.com/365986a132ccd6a44c23a9169022c0b5c890c387/68747470733a2f2f73332e616d617a6f6e6177732e636f6d2f6769746875622f726962626f6e732f666f726b6d655f72696768745f7265645f6161303030302e706e67" alt="Fork me on GitHub" data-canonical-src="https://s3.amazonaws.com/github/ribbons/forkme_left_red_aa0000.png"></a>
+    <a target='_blank' style="position: fixed; top: 0; right: 0" href="https://github.com/javierbyte/img2css"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://camo.githubusercontent.com/365986a132ccd6a44c23a9169022c0b5c890c387/68747470733a2f2f73332e616d617a6f6e6177732e636f6d2f6769746875622f726962626f6e732f666f726b6d655f72696768745f7265645f6161303030302e706e67" alt="Fork me on GitHub" data-canonical-src="https://s3.amazonaws.com/github/ribbons/forkme_left_red_aa0000.png"></a>
 
     <script>
       (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){