When everything's ready for prime time, there will be a stable release in the Chrome Web Store.
A packed, unstable version will always be available via the Downloads link above.
If you'd like to pack it from the source by yourself to ensure you have the latest version, use the following:
git clone http://github.com/brymck/vim_ratings cd vim_ratings install\windows
Linux (tested on Ubuntu)
git clone http://github.com/brymck/vim_ratings cd vim_ratings install/linux.sh