consider fetching from git repo

These recipe's would not be stable releases, but the current HEAD of a git repo.
The version name could be "HEAD" or "head" or "commit sha"
and URL could be:  https://github.com/tlmquintino/cookup.git
We would have to skip checksums for these.
Homebrew has a similar tap "head-only".

It would be great to install cf3 in this way.
