Update phantomjs dep to install on Yosemite.

This requires the latest code from HEAD, rather than a released version via homebrew, since the latest version will not ever compile on Yosemite. See https://github.com/Homebrew/homebrew/issues/29988
Stop expecting a binary from the coffee-script install

We don’t really need to check this, since Babushka’s NpmHelper will ensure the package is installed.
Add some `nodenv rehash` calls after various operations

I’m not 100% sure this helps, but it’s in here just in case.
Use `after` instead of `met` for printing out the bootstrapping info
Tidy comment