Concoure pipeline - Create a BOSH release tarball and save to S3

Creates a dev release of a BOSH release from its git repo and uploads to S3 as a tarball.

Example credentials.yml:

aws-bosh-init-bucket: my-bucket
aws-access-key-id: ACCESS
aws-secret-access-key: SECRET
aws-region-name: us-east-1

fly c -c pipeline.yml --vars-from credentials.yml \
  --var git-bosh-release-branch=develop \
  --var git-bosh-release=https://github.com/concourse/concourse