Implement 'integer-valued?', 'rational-valued?', and 'real-valued?' in Scheme

[Katie Burke]

scheme>>> integer-valued? 1901
Traceback (most recent call last):
File "stdin", line 1, col 1
RunTimeError: unbound variable 'integer-valued?'
scheme>>> rational-valued? 1901
Traceback (most recent call last):
File "stdin", line 1, col 1
RunTimeError: unbound variable 'rational-valued?'
scheme>>> real-valued? 1901
Traceback (most recent call last):
File "stdin", line 1, col 1
RunTimeError: unbound variable 'real-valued?'