Use my new [lscolors](https://github.com/sharkdp/lscolors) crate instead
of the internal `lscolors` module
- Speeds up `LS_COLORS` querying, leading to a nice 25% performance
improvement when
- Adds support for 24-bit colors and background colors
closes#368closes#363
This PR splits `internals.rs` into the `internal` module with multiple
files, and moves `FdOptions` into `opts.rs`.
The main motivation behind this is to move logic for constructing
`FdOptions` out of the main function and more readable and easier to
understand in the `opts` module. The goal will eventually to be able
to write `FdOptions::from(matches)` and have the options constructed.
Previously, the constants defined in `src/exit_codes` weren't being
used, and the constants for exit codes were being redefined in the
`internals` module.
This PR removes the exit code consts and instead uses an enum defined in
`src/exit_codes`. This centralizes the definitions of exit codes making
them easier to modify and keep track of.
