This work refactors the rabbitmq module to create rabbitmq::install, and
modernize aspects of the module.  Everything from specs to the README
is affected by this work.

The overall intent is to make it so that it works on Redhat as well as
Debian which fails currently due to duplicated resources.  Many new
features are added, such as `erlang_manage` to optionally use an
external erlang module to install erlang (this module no longer touches
erlang).
Remove relversion as a parameter and just build it out from $version.
Add framework for rspec-system tests.
Merge pull request #71 from apenney/refactor-installation

Refactor installation/few other bits.
Adding ability to configure cluster node type

Deprecating cluster_disk_nodes in favor of cluster_nodes and cluster_node_type
Updating README to reflect cluster node changes
Updating tests to handle cluster config changes