Libraries that are not available via yarn / the npm registry, are checked into git in the vendor folder.

Currently this affects the following libraries:

Version: 20140814

The closure-compiler is available on npm, but not the version we are using.

Version: 0.2.4

This project has never been published to npm.

If a different version becomes available, it must be manually downloaded and replaced in the repository.

Should yarn support requiring zip archives in the future (see yarn github issue: Zip support), we can remove the libraries from the repository and add them to the package.json.