Backport ruby-hiera-eyaml to Ubuntu Precise

Update `debian/changelog` and `debian/control` to backport the Utopic
package to Ubuntu.
Remove dependency on ruby-hiera

Hiera is provided by the Puppet Labs `hiera` APT package and no
`ruby-hiera` package exists for Precise, so remove the dependency.
Relax gem2deb dependency

The latest available `gem2deb` package available for Ubuntu Precise is
version `0.2.13`. The package still builds sucessfully with this
version, so relax the dependency.