Code coverage report

[Liquidsoul]

Code coverage is generated but it seems like it cannot be gathered by tools like codecov or even slather. This may be because this project is a OS X Command Line Tool and that it required me to add all the source files to the Unit test target. I looked at another swift command-line tool SwiftLint to see how they have set up the project and apparently, it's an OS X App from which they extract the executable to use it from the command line. Maybe it the way to go, maybe not...