SuckerPunch for Rails (Rails 4.2). These are the only changes I needed to get started

Gemfile

# add this line to your `Gemfile`:
gem 'sucker_punch'

sucker_punch.rb

# config/initializers/sucker_punch.rb
Rails.application.configure do
  config.active_job.queue_adapter = :sucker_punch

  # if you want to use Sucker Punch version 2.0.0+ with Rails < 5.0.0, be sure to
  # include the backwards compatibility module in an initializer:
  require 'sucker_punch/async_syntax'
end