calling fib on: 5
	calling fib on: 4
		calling fib on: 3
			calling fib on: 2
				calling fib on: 1
				calling fib on: 0
			calling fib on: 1
		calling fib on: 2
			calling fib on: 1
			calling fib on: 0
	calling fib on: 3
		calling fib on: 2
			calling fib on: 1
			calling fib on: 0
		calling fib on: 1
fib(5) = 8

calling tail on: 5
	calling tail on: 4
		calling tail on: 3
			calling tail on: 2
				calling tail on: 1
fibTail(5) = 8