There are going to be several `list` commands (e.g. `yubikey keys list`)
so this is a confusing name.
If we need more than one `readers` subcommand we can change this to be
`readers list` eventually.
Separately (in what probably should've been its own commit, mea culpa)
this adds slightly better usage.
Adds a `yubikey-cli` crate to the workspace, with a `yubikey` binary,
which presently provides a `list` command for listing detected readers.
Dependencies:
- `env_logger`: logging
- `gumdrop`: argument parsing
- `termcolor`: colored terminal output
As this repo now contains a binary, it also checks in `Cargo.lock`.
Carl Wallace