Include "rabbitmq::default" recipe

Otherwise configuration in /etc/rabbitmq isn't generated.
Set disk_free_limit to 50MB

Otherwise defaults to 1GB which may be too much for virtual
environments. Changes will only take effect after a restart since there
is no way to reload configuration at runtime.
Merge pull request #23 from saschpe/release/roxy/master-rabbit-fixes

Release/roxy/master rabbit fixes