[Rust] Implementing fmt::Debug trait for Vector class.

// Overloaded debug string
impl<T> fmt::Debug for Vector<T> where T: Copy + fmt::Display + num::Num {
    fn fmt(&self, f:&mut fmt::Formatter) -> fmt::Result {
        let mut s = String::new();

        s += "[";

        for i in 0..(self.vec.len()) {
            s += &format!("{}", self.vec[i]);

            if i < self.vec.len() - 1 {
                s += ", ";
            }
        }

        s += "]";

        // Write string to formatter
        write!(f, "{}", s)
    }
}