Proper error message for missing argument for parameters

[suntong]

When the required argument is missing from the cli parameter, cli should point that out, instead of error out on something else:

$ go run 001-hello.go -a
ERR! `` couldn't converted to an uint value

Normal case shown here.

[mkideal]

Thanks. I have fix it, see commit 7259422

[suntong]

Yep. Thx!