Cleaner display of errors

Right now the error display is a bit crude:

   ./subcommands.js number add AA BB
    int: invalid int: AA
    int: invalid int: BB

```
Usage: testCli number add INT INT
add two integers

Arguments:
INT                 int value
INT                 int value

Options:
[--help, -?]        Display help about this program
[--version, -V]     Display the version of this program
```
