Fibonacci numbers are a sequence of integers, starting with 1, where the value of each number is the sum of the two previous numbers,
e.g. 1, 1, 2, 3, 5, 8, etc. write a function called fibonacci that takes a parameter, n, which contains an integer value, and have it return the nth fibonacci number. (there are two ways to do this: one with recursion, and one without.)