Add support for adding option to subcommand

[canmor]

Implements adding option to sub command, following is an example:

$program = new Commander();

$program
    ->version('0.0.1');

$program
    ->command('rmdir <dir>', 'remove dir')
    ->option('-r, --recursive', 'remove recursively')
    ->action(
        function ($dir) use ($program) {
            foreach ($program->_subCmds as $cmd) {
                if ($cmd->_name == 'rmdir') {
                    if ($cmd->recursive) {
                        // recursively implement goes here...
                    }
                    else {
                        // normal implement goes here...
                    }
                    break;
                }
            }
        }
    );

$program->parse($argv);