feat: initial CLI framework

[agaffney]

Fixes #2

[agaffney]

$ ./cardano-up 
Usage:
  cardano-up [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  version     Displays the version

Flags:
  -h, --help   help for cardano-up

Use "cardano-up [command] --help" for more information about a command.
$ ./cardano-up help version
Displays the version

Usage:
  cardano-up version [flags]

Flags:
  -h, --help   help for version
$ ./cardano-up version
cardano-up devel (commit ef07e74)