mention flipping to show back-side

Author: donpark

README.md

@@ -1,5 +1,6 @@
-This project is a heavily modified version of Zack Waugh's [Helveticards](http://zachwaugh.com/helveticards/index.html) with three notable differences:
+This project is a heavily modified version of Zack Waugh's [Helveticards](http://zachwaugh.com/helveticards/index.html) with following notable differences:
 
 1. Cards are scalable.
 2. Card size may be specific to individual cards or set of cards.
 3. Face cards have standard Anglo-American court images rendered from Chris Aguilar's [vectorized-playing-cards](http://code.google.com/p/vectorized-playing-cards/) SVG files.
+4. Cards can be flipped to show the back-side.