Update Sandstorm SPK download information (GitHub, not S3)

README.md

@@ -71,7 +71,7 @@ Deploy your own Rocket.Chat server instantly on [Scalingo](https://scalingo.com)
 ## Sandstorm.io
 [![Rocket.Chat on Sandstorm.io](https://raw.githubusercontent.com/Sing-Li/bbug/master/images/sandstorm.jpg)](https://apps.sandstorm.io/app/vfnwptfn02ty21w715snyyczw0nqxkv3jvawcah10c6z7hj1hnu0)
 
-_*Grab*_ the latest [Sandstorm SPK](https://s3.amazonaws.com/rocketchatbuild/rocket.chat-develop.spk) for testing on your own server.
+_*Grab*_ the [Sandstorm SPK for the latest Rocket.Chat release](https://github.com/RocketChat/Rocket.Chat/releases/latest) for testing on your own server.
 
 ## Sloppy.io
 Host your docker container at [sloppy.io](http://sloppy.io). Get an account and use the [quickstarter](https://github.com/sloppyio/quickstarters/tree/master/rocketchat)