created cask for packer

[meantheory]

Created cask for packer from
packer.io which is used to
package up machine images
for cloud services, vagrant,
etc.

[radeksimko]

Although we have some apps which are already present in homebrew (binary) too, it's afaik always case of differently bundled apps (dmg/pkg) which are not available in Homebrew (binary). This is de facto copy of the homebrew binary package = I personally don't see a reason to have this in cask repo when it's tap & install away while already having Homebrew.

Also check out related discussion: #4228

I'm leaving the final decision on any other @caskroom/maintainers

[meantheory]

I agree @radeksimko - I found out about the homebrew-binary tap about 20 minutes after I submitted this. Feel free to close and ignore.

[meantheory]

I will also say the script in homebrew-binary is a lot smarter as I know nothing about ruby.

[radeksimko]

@meantheory the binary stanza is just not too scalable, but there's a solution on the way...