Fix Bacon.fromArray(...).toString() output after subscription

```coffee
stream = Bacon.fromArray [1, 2, 3]
console.log stream.toString() # Bacon.fromArray([1,2,3])
stream.subscribe (->)
console.log stream.toString() # Bacon.fromArray([])
```

Another solution was to pass the second clone of the `values` array into `describe`, but I don't like unnecessary copying, especially when there is a really simple alternative.