Queues.clj

Taken from [here](http://blog.marrowboy.co.uk/2011/10/21/worker-queues-in-clojure/), recording so I don't lose it:

```clj
(defn new-q [] (java.util.concurrent.LinkedBlockingDeque.))

(defn offer! 
  "adds x to the back of queue q"
  [q x] (.offer q x) q)

(defn take! 
  "takes from the front of queue q.  blocks if q is empty"
  [q] (.take q))
```

```clj
(def example-queue (new-q))

;; background thread, blocks waiting for something to print
(future (println ">> " (take! example-queue))) 

;; the future-d thread will be unblocked and ">> HELLO WORLD" is printed.
(offer! example-queue "HELLO WORLD") 
```