beep.rs

Play an indefinite tone of a given frequency.

For instance:

```rust extern crate beep; extern crate dimensioned;

use std::{thread, time}; use beep::beep; use dimensioned::si;

fn main() { beep(440. * si::HZ); thread::sleep(time::Duration::frommillis(500)); beep(si::Hertz::new(880)); thread::sleep(time::Duration::frommillis(500)); beep(0. * si::HZ); } ```