Add support for Fedora 18 to install_puppet.sh.

Fedora 18 uses puppet2.7 natively so we use that and gem install hiera.

Also updates our openstack_project:base manifest so that we upgrade
hiera via the gem provider.

Change-Id: I2ad8c1a81f9955f6de7812f72075fae84f7f7d7f
NOTE: puppetlabs only provides puppet > 3 for Fedora 18 anyway.
Reviewed-on: https://review.openstack.org/32449
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