install_puppet.sh introduced installation of just rubygems

We no longer install ruby1.8-dev , so for gardner we need
full ruby1.8-dev.

Update the docs so that we include this dependency.
hiera.sh also needs ruby1.8-dev, update hiera.sh to delivery that
update.

Change-Id: I63ba837bb5b3f08eb71f9dab3466b5729f28a8cf