I cooked up a little demo of a Slack bot running on Rails with React, that displays messages that you send to Slack, on a web page.
tl;dr Check out github.com/dblock/slack-bot-on-rails.
We start with a vanilla Rails app created via
rails new slack-bot-on-rails --skip-activerecord -T, in @d092f4ed.
Slap on top a React app that displays messages sent to Slack, in @9632e9f1.