Add script/console.

I wanted this today, and It Works For Me(tm) (I think).

```
$ ./script/console
irb(main):001:0> Feed.count
D, [2013-05-09T09:33:55.212105 #3071] DEBUG -- :    (1.3ms)  SELECT COUNT(*) FROM "feeds"
=> 2
```

Is `script/` a good place for this? Or somewhere else?