ReSwift Thunk Versions Save

Fixes:

• Fix Carthage build error (#44) - @DivineDominion, @mjarvis

Breaking API Changes:

• Drop support for Swift 3.2, 4.0, and 4.1. (#45) - @shawnkoh, @mjarvis
• Drop support for iOS 8 (#45) - @shawnkoh, @mjarvis

Other:

• Rename SwiftPM library to ReSwiftThunk, this makes naming consistent across all package manager (Cocoapods, Carthage and SwiftPM) (#42) - @jookes
• ExpectThunk's methods dispatches and getsState no longer have @discardableResult return values (#40) - @xavierLowmiller

API Changes:

• Renames createThunksMiddleware to createThunkMiddleware and adds deprecated forward for createThunksMiddleware (#20) - @fbernutz

Other:

• Adds ExpectThunk testing helper and corresponding CocoaPods subspec (#19, #37) - @jjgp, @okaverin
• Adds SwiftPM support (#21) - @jayhickey
• Require ReSwift 5.0 (#28) - @DivineDominion
• Specify all officially supported Swift versions in podspec (#38) - @okaverin

API Changes:

• Renames ThunkAction to Thunk
• Renames ThunkMiddleware() to createThunkMiddleware()
• Adds deprecated forwards for ThunkAction and ThunkMiddleware()

Other:

• This project has been migrated from https://github.com/mikecole20/ReSwiftThunk/ along with some backwards-compatible API changes documented above.