This is actually an outdated way of doing Node things. The instructions should simply be:

    npm install

Then to add this to your bash profile:

    # Get the bin for any local NodeJS module on cwd.
    PATH="./node_modules/.bin/:${PATH}"

And for that to work we'll need a package.json like Zamboni https://github.com/mozilla/zamboni/blob/master/package.json

This is a good opportunity to update webpay, could you make that change?