Fix breakage from yum::epel becoming yum-epel.  Lots of small cleanup too

yum::epel is no more so any cookbook depending on this and yum will fail when using chefspec or test-kitchen.  Switch to yum-epel instead
Expand RHEL family platform support with platform_family usage
Run the cookbook through rubocop for style fixes
Added recipes headers
Expand the Readme a bit
Use strings to define modes so that Ruby 2.0 doesn't freak out
Support newer RHEL 5 releases (5.9 / 5.10)