Add comment regarding nonblocking_redis
Drop 1.9.3 from travis since sidekiq deprecated it
Update dependency requirement for sidekiq and release new version
Remove old Heroku reference

[Heroku uses 2.8 now](https://devcenter.heroku.com/articles/redistogo#redis-2-8). Good to keep the requirement's in there obviously, but there's no need to call out Heroku specifically anymore.
Merge pull request #44 from lukechesser/master

Remove old Heroku reference