* Require Swift 5.0 to build
* Update CI
* Stop testing with Swift 4.x & Xcode 10.0/10.1
* Use official Swift docker image instead of norionomura's
* Use Xcode 10.3 as latest stable version
* Update READMEs
* Fixup xcodeproj
* Fixup CI Swift container image tag
* Fixup changelog