Add penguin resource

[markhobson]

Let's add a new sub-resource of queue to manage the 'penguin' lock:

/queue/:id/penguin

The operations would be:

• GET: obtain the name of the user with the penguin for this queue
• PUT: set the name of the user with the penguin for this queue
• DELETE: release the penguin for this queue

This would currently be insecure, since any user could release the penguin, but this will be addressed in future with user authentication.