Correct example for ferris_says on mac

[wilfredvaz]

The correct ferris_says for mac

refer below

extern crate ferris_says;

use ferris_says::say;
use std::io::{ stdout, BufWriter };

fn main() {
let width = 24;

let mut writer = BufWriter::new(stdout());
say("Hello fellow Rustaceans!", width, &mut writer).unwrap();

}