Change the default behaviour of Camelized props

[BookOfGreg]

• [x] I have another issue to discuss.

---

In #409 we allowed an opt-in config to change from snake_case to camelCase. In #556 we exposed the function externally incase it needs to be used.

I believe it may be time to switch to camelCase as the default, this is because the generator makes camelCase components.

$ rails g react:component post snake_case:string
#      create  app/javascript/components/Post.js

propTypes: {
    snakeCase: PropTypes.string
  }

This would be part of a v3 release due to breaking backward compatibility if we chose to go for it.