I'm on react-native 0.44 and if I'm missing something new in the recent updates, I apologize. Thanks to @codesinghanoop for his recent fix to parallelize downloads. My app loads twice as fast now!
I've had to add the following to RNFSPackage.java to make things work using the master branch.
@Override
public List<Class<? extends JavaScriptModule>> createJSModules() {
return Collections.emptyList();
}