prepend current time

```js
debug('init', {a:1, b:2});
debug('init', 1, 2);
debug('init', 'testing', +new Date());
```

![screen shot 2014-08-07 at 6 21 34 pm](https://cloud.githubusercontent.com/assets/1265628/3840942/0dd7fbaa-1e25-11e4-8845-ea404c0b2e4d.png)