Nuke 0.2.1

• Add ImageCollectionViewPreheatingController (yep)
• Add Image Preheating Guide
• Add preheating demo

Nuke 0.2.0

Major

• Optional Alamofire integration via 'Nuke/Alamofire' subspec
• Optional FLAnimatedImage integration via 'Nuke/GIF' subspec
• More concise API
• Add image filters to ImageRequest
• Add ImageManaging protocol
• Add ImageDecoderComposition
• Add ImageProcessorComposition
• watchOS
• Add convenience functions that forward calls to the shared manager

Minor

• Use ErrorType
• Add removeAllCachedImages method
• ImageRequest userInfo is now Any? so that you can pass anything including closures
• ImageResponseInfo now has userInfo: Any? property
• ImageResponseInfo is now a struct
• CachedImageResponse renamed to ImageCachedResponse; userInfo is now Any?
• Multiple improvements across the board