`brew install node` – what about npm?

Ref. https://github.com/mathiasbynens/dotfiles/blob/90a0c750bb6b8ee230be32202c407a87e0fb3d73/Brewfile#L40

`brew install node` might not install `npm` anymore in the future: https://github.com/Homebrew/homebrew/pull/27479

Alternate solution: https://gist.github.com/isaacs/579814#file-yet-another-option-sh
