Show --help for invalid command

[rogeriochaves]

Thanks to commander.js we already have a --help, which shows this:

» elm generate --help

  Usage: elm-generate [options] [command]

  Options:

    -h, --help               output usage information

  Commands:

    app <name>
    route <Name>
    component <Name>
    component-view <Name>
    component-types <Name>
    component-update <Name>

But if I run an invalid command it outputs nothing:

» elm generate foobar

It would be better to show the --help instead