Redhat support

Add GlusterFS Epel repo, and install GlusterFS on RedHat based distro.

Tested on CentOS 6.5 and 7.0
It's a lot of options with the namespace `node['yum'][repo]`, in your attribute files I cannot see those defined attributes.
By example node['yum']['glusterfs-epel']['proxy_password'] is missing. I assume it's done in order to allow to tune each and every parameters of the repos if we need to.