Release version 4.1.2.

Set version to 4.1.1

Readme: update with new functionality.

Also fix some other stuff.

CocoaPods: set version to 4.1.

Travis: use osx_image xcode9.3.

Release version 4.0.2, set Swift version to 4.0.3.

Fix indentation.

Merge swift4 into master

Release SwiftShell 3.0.

At long last.