Merge pull request #32 from mperham/master

RDoc enqueue
Update README.md

beanstalkd and rabbitmq are MQ servers, they aren't something that would integrate directly with Rails and ActiveJob.  That's like saying we want an adapter for Redis, when really you want adapters for Resque, Sidekiq, etc.

Sneakers is the latest Ruby job system using rabbitmq.  I don't know of a modern beanstalkd system for Ruby, Stalker is pretty dead these days.  I added QueueClassic because it's reasonably popular on Heroku for the "postgresql only" crowd.
Merge pull request #33 from mperham/patch-2

Update wanted list
Implemented queue_classic adapter
Merge pull request #34 from cristianbica/queue_classic-adpater

queue_classic adapter