Add support for EL 5

Options are documented at
http://www.centos.org/docs/5/html/5.2/Deployment_Guide/s2-sysconfig-clock.html
Support Puppet v3.6.0
Stop requiring rubygems as that is an anti-pattern
Fix quoting in Gemfile

no variable interpolation, so using single quotes
Merge pull request #3 from ghoneycutt/support_el5

Support el5