Implement 'max' and 'min' in Scheme

[Katie Burke]

max should the maximum of real1 real2 ...
min should return the minimum of real1 real2 ...
http://www.scheme.com/tspl4/objects.html#./objects:s107

This example should return 4.

(max 4 -7 2 0 -6)

Traceback (most recent call last):
File "stdin", line 1, col 2
RunTimeError: unbound variable 'max'

This example should return -7.

(min 4 -7 2 0 -6)

Traceback (most recent call last):
File "stdin", line 1, col 2
RunTimeError: unbound variable 'min'

[Doug Blank]

Scheme: implement max and min, fixes #35

→ <<cset f4f454ad5101>>