Add tests for isRefreshing <~ isExecuting binding.
Add tests for isRefreshing <~ isExecuting binding.

ohwutup/ReactiveCocoa,ohwutup/ReactiveCocoa,walkingsmarts/ReactiveCocoa,walkingsmarts/ReactiveCocoa,calebd/ReactiveCocoa,calebd/ReactiveCocoa,ohwutup/ReactiveCocoa,walkingsmarts/ReactiveCocoa,calebd/ReactiveCocoa