Simplify and correct hiera install documentation

The documentation for hiera had the user add the repo and then remove it just
to install hiera, but that's now done in a previous step to use newer versions
of the puppet packages from the puppetlabs repos. The yaml file is also now
installed by puppet. Also collapsed all hiera documentation into the puppet
master section.

Change-Id: I00ab3cd12798295827ae25a623d246f7abf9a8df
Reviewed-on: https://review.openstack.org/20077
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins