Facter 1.6 doesn't have operatingsystemmajrelease fact

Facter 1.6.18 is the latest facter release in EPEL so lets target that.
Modulo operator wasn't introduced until 3.2

Perhaps revisit this in the future. For now we'll assume that if someone is installing with more than 3
datastore nodes they know what they're doing.
Merge pull request #328 from sdodson/facter16

Some compatibility fixes for Puppet 2.7 and Facter 1.6