ConcurrencyKit Release 0.7.2

[justinethier]

A new release is available:
https://github.com/concurrencykit/ck/releases/tag/0.7.2

We should evaluate to see how well it works with Cyclone.

[justinethier]

Need to take a closer look at this, because 0.7.2 is causing the MacOS build to break ;(