impl SampleRange for std::time::Duration

[canndrew]

This would be nice to have and should be simple to implement.

[pitdicker]

I agree this could be nice, but is it worth the extra API over creating a Duration from an integer?

use rand::thread_rng::thread_rng;
use std::time::Duration;

let mut rng = thread_rng();
let range = Range::new(0u64, 10_000);
let duration = Duration::from_millis(range.sample(&mut rng));

[canndrew]

I think so. It's easy to add one more impl.

[dhardy]

Okay, PR please?