Choices and files

Adds a Choice type for selecting values from a small set and InFile and OutFile for file options.

New Values system

This is a more flexible and hopefully more stable way to handle argument values, especially because a user can define his or her own.

Usage fix

Usage was set recursively, meaning that subcommands would show the doc from their parents.


Commands now created from a specification

cli now uses reflection to extract flags and positional arguments from a type, and the NewCommand function uses a spec to setup a new command structure.

First versioned release

v0.0.1

other variadic types