Add redhat support

Hi!

We're looking to split out the erlang handling from the puppetlabs-rabbitmq module and I found your erlang one on the forge.  I know this is a fairly large PR out of nowhere but I was aiming to add support for RHEL5/RHEL6, and make the Debian support a little more parameter based so people can overwrite it if needed.

I've tested this PR on:

Ubuntu 12.04
Centos 5.9
Centos 6.4

As well as via the specs and it seems like it still works as intended. I actually think I may have fixed some of the key handling stuff on Debian as well as it wasn't pulling in from the right place.

If you're OK with this PR and merge it (and hopefully do a forge release) then I'll continue on my work to make the rabbitmq module rely on this one if you're OK with that!