Initial `SignalProducer.swift` documentation trimming
Initial `SignalProducer.swift` documentation trimming

smilypeda/ReactiveCocoa,walkingsmarts/ReactiveCocoa,ikesyo/ReactiveCocoa,calebd/ReactiveCocoa,ohwutup/ReactiveCocoa,walkingsmarts/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,sandyway/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,smilypeda/ReactiveCocoa,smilypeda/ReactiveCocoa,calebd/ReactiveCocoa,victorlin/ReactiveCocoa,sandyway/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,ohwutup/ReactiveCocoa,sandyway/ReactiveCocoa,ohwutup/ReactiveCocoa,walkingsmarts/ReactiveCocoa,victorlin/ReactiveCocoa,victorlin/ReactiveCocoa,ikesyo/ReactiveCocoa,calebd/ReactiveCocoa