Add Ruby Enterprise Edition Ubuntu knife bootstrap target

As we're still on Ruby 1.8.7, we find the Ruby Enterprise Edition packages that Phusion provide allow us to update Rubygems while still using a 'packaged' Ruby.

As such I created a bootstrap to install REE on an Ubuntu Lucid system and then use that to install chef rather than risk having multiple Ruby versions on a system without using RVM.

It downgrades to Rubygems 1.3.7, as that seems to, well, work for everything.

I hope you find this useful!