~/$ python3
    Python 3.6.3 (default, Oct  4 2017, 06:09:05) 
    [GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import fib
    >>> fib.fib_tail_recurse(1000)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/Users/kerkeslager/fib.py", line 4, in fib_tail_recurse
        return fib_tail_recurse(n, i+1, cur_sum+prev_sum, cur_sum)
      File "/Users/kerkeslager/fib.py", line 4, in fib_tail_recurse
        return fib_tail_recurse(n, i+1, cur_sum+prev_sum, cur_sum)
      File "/Users/kerkeslager/fib.py", line 4, in fib_tail_recurse
        return fib_tail_recurse(n, i+1, cur_sum+prev_sum, cur_sum)
      [Previous line repeated 994 more times]
      File "/Users/kerkeslager/fib.py", line 2, in fib_tail_recurse
        if i >= n:
    RecursionError: maximum recursion depth exceeded in comparison
    >>>