Changed the loop variable to an int

I changed the loop variable to an int (from a long int). I also wanted to point out that with this change, the iterative and recursive approach takes approximately the same amount of time. I thought you'd like to know. 

recursive fib: 7921 ms, validation: 6744
iterative fib: 8078 ms, validation: 6744
analytic fib: 104297 ms, validation: 6744
analytic opt fib: 55282 ms, validation: 6744