Add download badge

Author: luin

README.md

@@ -43,4 +43,4 @@ $ ./Medis.app
 * Simply star this repository :-)
 * Help us spread the word on Facebook and Twitter
 * Contribute Code! We're developers!
-* Medis is available on the Mac App Store as a paid software. I'll be very grateful if you'd like to buy it to encourage me to continue maintaining Medis. There are no additional features comparing with the open-sourced version, except the fact that you can enjoy auto updating that brought by the Mac App Store.
+* Medis is available on the Mac App Store as a paid software. I'll be very grateful if you'd like to buy it to encourage me to continue maintaining Medis. There are no additional features comparing with the open-sourced version, except the fact that you can enjoy auto updating that brought by the Mac App Store. <br> [![Download on the App Store](http://getmedis.com/download.svg)](https://itunes.apple.com/app/medis-gui-for-redis/id1063631769)