Use the operatingsystemmajrelease fact instead of operatingsystemelease for the sub-case statements in params.pp.
Add CentOS 7 as a supported OS to metadata.json.
Added a mention of CentOS 7 support to the README.
CHANGELOG entry for CentOS 7 support.
Added blurbs to the README about required Puppet and Facter versions.
Switch around the CentOS download links in the README since version 7 is what is available on the main site and you have to go to the wiki for 6.x download links.