rjvId may be collided

[rjvId](https://github.com/microlinkhq/react-json-view/blob/master/src/js/index.js#L34) may be collided.

When it happened, two JsonView may influence each other.

We may add a hash to prevent collision.

```diff
-rjvId = Date.now().toString()
+rjvId = Date.now().toString()+Math.random().toString(36).slice(2)
```