Create a release for our Travis to download instead of cloning the git repo

Since cloning this git repo is the slowest part of our Travis CI builds, we could improve performance by making a release with only the necessary files included for the `deps` target to download.

Start by tracing the Travis CI configuration and the deps target to identify how the repository is currently cloned and which files it needs. Define the release contents and update the deps download path so it uses that release instead of cloning; done means the Travis build can obtain the required files through the release.

Written by the indexing model from the issue text.