[WIP] CentOS/RedHat Support

This is a work in progress. Submitting PR now for discussion purposes and to make sure I stay on a track that you will accept.

Please give me initial feedback and let me know if you like what you see so far.

A couple of notes:
# I added a few parameters. The `repo_version` parameter I think is necessary for yum repos specifically. It's set up such that the 5.5 repo actually points to 5.5 latest, currently 5.5.37. 5.5.37 has a bug that causes clustering to fail. Setting `ensure => '5.5.36'` wouldn't work since the yum repo at 5.5 only has 5.5.37. Allowing the user to specify a `repo_version => '5.5.36'` will then enable them to install MariaDB 5.5.36. 
# I removed the run stage since those don't work well in everyone's environments. Specifying a dependency that the repo class run before the package class seems fair I think.
# I added the ability to set `repo_manage => false` so users can opt to manage their repos through an external mechanism.

Given all of the above items I think I've done a good job of retaining the current behavior so nothing breaks for existing users. This is not currently fully tested so if something is broken I will fix it shortly :)