Update rabbitmq check to support number of queues

We have had instances where the number of queues grows uncontrollably.
This change modifies the rabbit check plugin so that you can specify
either queue length or number of queues.
Enable number of rabbitmq queues check

Now that I have updated the rabbit queues check to check number of
queues, enable this in Ursula.
Update check-rabbitmq-queues to parse via Ruby

We had previsously been shelling out to parse the output of the rabbit
queues check.  As this was getting a bit hairy, do this with Ruby
instead.
Fix broken whitespace issues

I was developing on a box that didnt have a proper vimrc. Hence my
whitespace problems - fix that here.
Remove uneccessary io.close

The io.close is implicit when the block terminates.
Merge pull request #423 from craigtracey/numqueues

Check the number of RabbitMQ queues