phstc/shoryuken — pull request #25 by petergoldstein (2014-12-14 23:19:12+00:00)
Title: Fix racy shutdown

This is basically a port of Sidekiq PR #2056 - https://github.com/mperham/sidekiq/pull/2056 . It includes:

1. Upgrading the Celluloid version
2. Adding a Condition variable to address the racy shutdown problem
3. Updating a spec to account for the change in the Shoryuken::Manager initialize method signature.