Add chapter on commandline arguments

Please let me know if you think the example should be more verbose.
No: https://github.com/uutils/coreutils/blob/master/LICENSE


2014-06-30 20:46 GMT-04:00 Jorge Aparicio <notifications@github.com>:

> In LICENSE-ECHO:
>
> > @@ -0,0 +1,18 @@
> > +Copyright (c) Jordi Boggiano
>
> This doesn't have a copyright year?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/japaric/rust-by-example/pull/76/files#r14384232>.
>