Packer v0.8.6をダウンロードした.
# Packer v0.8.6をダウンロードした.
$ brew upgrade packer
> Error: packer-0.7.5 already installed
$ brew cask install packer
> ==> Downloading https://dl.bintray.com/mitchellh/packer/packer_0.8.6_darwin_amd64.zip
> ... (略)
$ packer version
> Packer v0.8.6