Large number of misc fixes

Update chefignore and gitignore to match those used in most Chef cookbooks
Bump Ruby to 2.1.5 since 1.9.3 is no longer supported as of Chef 12
Add support for additional RHEL based distros
Switch mode over to a string to support Ruby 2
Update references to Opscode to be Chef Software and update copyrights
Add a rubocop config and run rubocop
Add more platforms to the Kitchen config