Regression: ETA calculation shows "00:00:00" for the first ten ticks.

[sharkdp]

indicatif 0.9 used to show a good ETA estimate after the the first .inc(1) update, but 0.10 seems to require around ten .inc(1) calls until it shows the first ETA that is non-zero.

In my use case, a single "tick" can easily last multiple seconds, so this is easy to notice. Minimal example to reproduce:

extern crate indicatif;

use std::thread;
use std::time::Duration;

use indicatif::{ProgressBar, ProgressStyle};

fn main() {
    let count = 15;
    let pb = ProgressBar::new(count);

    pb.set_style(
        ProgressStyle::default_bar()
            .template("{wide_bar} Elapsed: {elapsed_precise}, ETA: {eta_precise}")
    );

    for _ in 0..count {
        thread::sleep(Duration::from_millis(1000));
        pb.inc(1);
    }
    pb.finish_with_message("done");
}

After 9 seconds, it still shows:

███████████████████░░░░░░░░░░░░░ Elapsed: 00:00:09, ETA: 00:00:00