The good-enough? test produces very inaccurate results for very small numbers.  For example,
calculating the square root of 0.0001 would result in an answer of 0.01.  However, running
the sqrt function gives a result that is ~3.2 times larger than the correct result.

> (sqrt 0.0001)
0.03230844833048122


Testing for very large numbers (e.g. see below) produces a slightly different problem, in
that the operation never terminates.  This is due the good-enough? function being unable to
guess large numbers to a precision of 0.001.

> (sqrt 1e15)
Error: Never Terminates

Alternative Version 1:
(define (good-enough? guess x)
  (< (/ (abs (- (improve guess x) guess)) guess) 0.001))

  
Alternative Version 2:
(define (good-enough? guess x)
  (cond
    [(and 
      (< (abs (/ (improve guess x) guess)) 1.001)
      (> (abs (/ (improve guess x) guess)) 0.999))
     true]
    [else false]))