Update MacOS Java installation guide in Tutorial

The existing command in the tutorial is deprecated. Please consider updating it to the latest one for avoiding confusion and misleading newcomers.

Author: WANG, Chen

README.md

@@ -47,7 +47,7 @@ Before proceeding further with this document, make sure you have the following p
 
     For macOS:
     ```bash
-    brew tap caskroom/versions
+    brew tap homebrew/cask-versions
     brew update
     brew cask install java8
     ```