The script handles bumping up the version number, committing, tagging
and updating the Homebrew formula. The last step requires `hub` to be
installed in order to submit a pull request to Homebrew.
/cc @sferik @hsbt
[ci skip]
When new Ruby definitions get added, our current CloudFront mirror may
get out of date. This adds a task to the CI process that detects
added/changed package URLs and uploads them to our S3 bucket.
Fixes#392, references #395