Add ability to configure installed openstack version

perform a hiera lookup for the openstack_version
to use to setup the appropriate packages(for ubuntu).

Ensure that setup/hosts.pp is run before (and not from
within) setup/os.pp. This is b/c hiera is not
required to be installed before the os specific
setup manifest is run.
move wget code to be before node blocks

just to organize things.
Merge pull request #59 from bodepd/control_ubuntu_os_version

Control ubuntu os version