Update stlrc to use TerminalKit

[SwiftStudies]

CommandKit is heavy and fundamentally hard to understand. TerminalKit is simpler (and somewhat less powerful) but is more than enough and will enable easier extension.

https://github.com/SwiftStudies/TerminalKit

[nrivard]

Maybe i'm misinterpreting this issue (it is also 2 years old) but you should perhaps look into ArgumentParser: https://swift.org/blog/argument-parser/

this is managed by swift.org and should take boilerplate out of commandline tool argument parsing.

[SwiftStudies]

You aren't... I think you are right that this is the way to go