Function min_element 

pub fn min_element<T: Ord>(vec: &[T]) -> Option<&T>

Find the minimum element in the vector

Example:

    use r_unit::vec;

    let vector = vec![1, 2, 3, 4];

    if let Some(min) = vec::min_element(&vector) {
        println!("The minimum element in the vector is: {}.", min);
    } else {
        println!("The vector is empty.");
    };