Swift 4.2.

• Update to Swift 4.2.
• Update to SwiftShell 4.1.2.
• Use Carthage for dependency.
• Add setup.sh.

0.2.1

• Add missing "products" section to Package.swift.
• Update to SwiftShell 4.1.1.
• Import FileSmith as "testable" in unit tests.

Swift 4.1

Update to Swift 4.1 and SwiftShell 4.1.0.

0.1.0

Should be usable now.