Use the builder to generate your own Proper script, complete with requested dependencies.
Navigate to directory where you have downloaded your Proper script:
cd ~/<location-of-directory>/proper
If you take a peek inside the /manifest directory, you should see a list files that correspond to the list of available origins (npm, brew, cask, mas, composer).
To install all items in manifest, call the entry script directly:
sh proper
There are a list of known issues, however if you uncover any issues not mentioned there, please file an issue.