Provide example with react-rails

[justin808]

We can allow an ENV value to switch between the two gems.

However, let's get dependencies updated first for this repo.

[ahangarha]

I spent some time on this feature. RWRT uses so many features from ReactOnRails that make it either impossible to pointless to add a switching feature to this project.

For such a switch, we need to implement the missing features (let's say, shared redux store) in this project. If it is one feature, it is understandable; but to add all ROR-specific features here, I see no point.

[justin808]

See https://github.com/shakacode/react-rails-example-app