4.0.0 - Hummingbird

Added

• Added support for scheme pre-actions and post-actions #217 by @kastiglione

Changed

• Breaking: Changed the return type of some helper functions that create or fetch PBXObjects to be ObjectReference, which includes the reference as well as the object #218 by @yonaskolb
• Breaking: Changed some Int properties into Bool or UInt #221 by @yonaskolb
• Changed the writing of some properties to minimise diffs when opening projects in Xcode #220 by @yonaskolb