Basic RedHat Support

Changes:
=======

* Created a `vars` file for portability to RedHat flavored systems. 
* Parameterized the inet_interfaces variable such that it is configurable in playbooks.
* Changed the banner to use the system FQDN to pass reverse DNS validation

I've tested this on a CentOS/EL6 system and it passes [MXToolbox diagnostics](http://mxtoolbox.com/diagnostic.aspx).