RNRF only showing a spinning circle after trying to upgrade

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

- react-native-router-flux v4.0.6
- react v16.6.0-alpha.8af6728
- react-native v0.57.8

### Expected behaviour
Main Router is displayed when launching the app

### Actual behaviour
A white screen and spinning/loading circle is shown. No errors on screen, node, and js remote debugging is not able to connect if I try to do that.

### Steps to reproduce
For non-obvious bugs, please fork this component, modify Example project to reproduce your issue and include link here.
1. react-native run-android

I had previously been working with "react-native-router-flux": "^4.0.0-beta.31", but that had some bugs that I couldn't work around. I changed the RNRF version to "^4.0.6", deleted the node_modules folder and ran npm install. When trying to launch the app again this happened. I tried to upgrade RNRF in the past but ran into this same wall back then. There's more than a good chance I screwed something up on my own but I couldn't find anything saying a specific version of RN or React was needed for RNRF or anything like that.

This is probably meaningful: if I reset my package.json to read the original version, beta 31, delete the node_modules folder and run npm install it does not go back to working. It still only shows me the spinning circle.

### Reproducible Demo

Stripped down to pretty much nothing:

const MainRouter = () => {
return (





({ main: { opacity: (2 - ratio) / 2 } })}
>







);
};