DUIX doesn't work in React with Hooks

If you are doing:

```js
useEffect(() => {
  duix.subscribe('user', setUser)
}, []);
```

The `setUser` function is going to get old in the following render.
We have to find a way to keep it simple, but fix it.

I think we should not create a `useDuix()`, because the idea is to keep DUIX as a state manager **based on events.**