add BigNum implementation

//

// Created by Ari Trachtenberg on 1/30/17.

// Originally written by Ari Trachtenberg on 1/30/17.

// Adapted for EC330.

//

#ifndef HW1_BIGNUM_H

#define HW1_BIGNUM_H

// Written by Prof. Ari Trachtenberg for EC330

#include <iostream>

#include <vector>

#include <string>