Adding ability to configure cluster node type

Deprecating cluster_disk_nodes in favor of cluster_nodes and cluster_node_type
Make sure we @ all variables to remove warnings.
Manual cherry-pick of cluster README fixes

This commit is essentially a hand port of
the commit a41a1dda6c5fedfcb28f88270fb7a58f379f787c
from Bryan Wyatt <brwyatt@gmail.com>
from master.

The merge conflict was so bad, that I decided to recraft the
commit.
Updating tests to handle cluster config changes
Revert "Add rabbitmq_exchange type and provider"

This reverts commit 95584a5a9eae6e8fb23263fb676d0cce966bad5a.

Conflicts:

	lib/puppet/type/rabbitmq_exchange.rb
	manifests/server.pp

This commit reverts a previous commit that added support for installing
rabbitmq admin.

I am reverting this patch b/c it does not work with rabbit 2.7.x (which
is what Ubuntu Precise currently ships with)

I ran into the folliwing problems with this patch:
  - it expects rabbitmq-plugins and rabbitmq-env to be in the current.
  - in its current form, it relies on defined variables default_user
  and default_pass to be defined in rabbitmq::server
Merge pull request #92 from bodepd/fix_rabbit_spec_tests

Fix rabbit spec tests
Merge pull request #93 from bodepd/revert_rabbitmqadmin

Revert rabbitmqadmin
merge upstream 2.x