Update to Sidekiq 3.x

@didil

All of the specs pass with this change.  Do you know anything else that would need to be done for this to work with Sidekiq 3.x?  

I did an integration test in my environment and was able to push a job into a queue and the job complete successfully. 

This *should* resolve https://github.com/didil/sidekiq-client-cli/issues/12