Add @Observable property wrapper and bump the CI to Xcode 11 / Swift 5.1 - #762

Add @Observable property wrapper and bump the CI to Xcode 11 / Swift 5.1#762

petrpavlik wants to merge 8 commits into

ReactiveCocoa:masterReactiveCocoa/ReactiveSwift:masterfrom

petrpavlik:masterpetrpavlik/ReactiveSwift:masterCopy head branch name to clipboard