impl shuffle fn based on Fisher-Yates

shuffle.rs

extern crate rand; 
use rand::Rng;

// Fisher-Yates shuffle
fn shuffle<T: Clone>(v: &mut Vec<T>) {
    let mut rng = rand::thread_rng();
    let s = v.len();
    (0..s).for_each(|i|{
        let q = rng.gen_range(0, s);
        v.swap(i, q);
    });
}