fn mutate(chromosome: &mut str) {
    let mut tmp_random = rand::random::<f32>();

    for mut i in chromosome.chars() {
        tmp_random = rand::random::<f32>();
        if tmp_random < MUTATE_RATE {
            println!("Mutating!");
            match i {
                '0' => i = '1',
                '1' => i = '0',
                _   => continue,
            }
        }
    }
}