REPLACE does not replace the proper route

### Version
Tell us which versions you are using:

- react-native-router-flux v4.0.6
- react v16.2.0
- react-native v0.53.3

### Expected behaviour

`REPLACE` does not work properly, it replaces wrong route.

### Actual behaviour

`REPLACE` to replace the proper route.

I think that this code is problematic here:
const routes = [...parent.routes.slice(0, index - 1), ...parent.routes.slice(index)];

Shouldn't it be this?
const routes = [...parent.routes.slice(0, index), ...parent.routes.slice(index + 1)];