test op will fail if 2 objects are ordered differently

Spec:
http://tools.ietf.org/html/rfc6902#section-4.6

Implementation:

``` javascript
    test: function (obj, key) {
      return(JSON.stringify(obj[key]) === JSON.stringify(this.value));
    },
```

It doesn't work if 2 arrays/objects are equals (from the RFC definition) but ordered differently.

```
JSON.stringify(['foo', 'bar']) === JSON.stringify(['bar', 'foo']); //false
```
