docs(readme) document some customization points

[rmosolgo]

I hope this will help people understand & improve react-rails! And help them find ways to extend it in the ways they want to, eg Flux-on-the-server, gon.

[vipulnsward]

I was playing around to use redux - vipulnsward@e240b64

I think, a new helper can be introduced if needed by someone, without affecting existing helper.
More tricky is the ujs handling.

[rmosolgo]

Oh, nice, that allows you to inject react_redux_state into the page, then load it up?

Yeah, I imagine if you need custom UJS you could just remove:

//= require react_ujs

And instead, require the custom UJS

//= require custom_ujs