Update release instructions

Homebrew split their repository.

RELEASE.md

@@ -88,24 +88,29 @@ Get the SHA256 of the tarball:
 shasum -a 256 vX.Y.Z.tar.gz
 ```
 
-Update the formula:
+Update the formula. You will need to fork https://github.com/Homebrew/homebrew-core.
 
 ```
+cd $(brew --repository)/Library/Formula
+git checkout master
+
 cd $(brew --repository)
 git checkout master
-git remote add YOUR_USERNAME git@github.com:YOUR_USERNAME/homebrew.git
+
 brew update
-git checkout -b exercism-vX.Y.Z
-brew edit exercism
-# update sha256 and tarball url
-brew audit exercism
+brew edit exercism # update sha256 and tarball url
 brew install exercism
+brew audit --strict --online exercism
 brew test exercism
+
+cd /Library/Formula
+git remote add YOUR_USERNAME git@github.com:YOUR_USERNAME/homebrew-core.git
+git checkout -b exercism-vX.Y.Z
 git commit -m "exercism X.Y.Z"
 git push --set-upstream YOUR_USERNAME exercism-vX.Y.Z
 ```
 
-Then go to https://github.com/Homebrew/homebrew and create pull request.
+Then go to https://github.com/Homebrew/homebrew-core and create pull request.
 
 Note that they really don't want any verbose commit messages or PR descriptions when all you're doing is bumping a version.