segmentio/yal — pull request #4 by juliangruber (2014-02-04 15:19:16+00:00)
Title: expose error messages

So:

```js
var err = new Error('message');
err.foo = 'bar';
log.error('oops', err); // => { foo: 'bar', message: 'message' }
// instead of { foo; 'bar' }
```

For perf: http://jsperf.com/make-property-enumerable