Right now this is just used for two things:
* Specifying folders for locarting parsers to use with `tree-sitter
parse` and `tree-sitter highlight`
* Specifying colors to use for `tree-sitter-highlight`
* Structure `cli` crate as both a library and an executable, so that
benchmarks can import code from the crate.
* Import macros in the Rust 2018 style.