ReactiveCocoa/ReactiveCocoa — pull request #1625 by tonyarnold (2014-12-16 03:38:03+00:00)
Title: Update requirements to iOS 6 and OS X 10.8

It looks like the Xcode project specifies a minimum or OS X 10.8 SDK, and uses iOS 6.0 only features (strong properties with a type of `dispatch_queue_t`)