Add initial markup for `Flatten.swift`
Add initial markup for `Flatten.swift`

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