Single page Rails 5 app

hello_world.rb

# gem install bundler
# ruby hello_world.rb

require 'bundler/inline'

gemfile do
 source 'https://rubygems.org'
 gem 'rails', '~> 5.0'
end

require 'action_controller/railtie'

class HelloWorld < Rails::Application
  routes.append do
    root to: 'hello#world'
  end

  config.secret_key_base = SecureRandom.hex(30)
  config.eager_load = false
  config.logger = Logger.new(STDOUT)
end

class HelloController < ActionController::Base
  def world
    render plain: 'Hello, World!'
  end
end

HelloWorld.initialize!
Rack::Server.start app: HelloWorld