Make ready for Ubuntu 14.04

package rubygems doesn't exist in Ubuntu 14.04

This workaround fixes this. Issue already created on original repository
(https://github.com/davidwinter/puppet-papertrail/issues/6)

Conflicts:
	manifests/init.pp
Merge pull request #6 from leifg/make_compatible_to_ubuntu_1404

Not working on Ubuntu 14.04