Install stack on macOS Sierra using homebrew

[xeoneux]

macOS Sierra warning: Homebrew's haskell-stack formula may not currently work on Sierra, so we suggest using the manual method above for now.

Is this issue in the docs resolved? I tried installing the haskell-stack formula on macOS Sierra and it installed the bottle perfectly.

[borsboom]

You're right, that's probably resolved now. A PR removing that warning would be welcome.