Nuke 8.4

• Fix an issue with RoundedCorners image processor not respecting the Border parameter – 327, Eric Jensen
• Add an optional border parameter to the Circle processor – 327, Eric Jensen
• Add ImagePipelineObserving and DataLoaderObserving protocols to allow users to tap into the internal events of the subsystems to enable logging and other features – 322, Abdallah Nehme
• Deprecate Nuke.Image to avoid name clashes with SwiftUI.Image in the future , add PlatformImage instead – 321
• Make ImagePipeline more readable – 320
• Update demo project to use Swift Package Manager instead of CocoaPods – 319