This project is a script sub-library and is part of a larger project managed as a Google-repo called "SCRIPT3" (or "s3" for short). S3 can be found here: https://github.com/mambrus/script3
To download and install any of s3's sub-projects, use the Google's "repo" tool and the manifest file in the main project above. Much better documentation there too.
Note that most of s3's sub-project files won't operate without s3 easily (or at all).