Fraction.divide tweak

Chris Ward provided this useful suggestion about the Fraction.divide
code:

"(a/b)/(c/d) == (a/b)*(d/c).
Instead of using expensive division operations, and commonly converting
one or both of the numerator and denominator into floats, simply invert
the divisor and call the multiply function."

I implemented the change and was happy to find an approximate 2.5x speedup
in division operations and an end to common rounding errors which had
plagued the implementation.

Thanks Chris!

fraction.js

@@ -201,23 +201,21 @@ Fraction.prototype.multiply = function(b)
     return a.normalize();
 }
 
-
 Fraction.prototype.divide = function(b)
 {
     var a = this.clone();
     if (b instanceof Fraction)
     {
-        a.numerator /= b.numerator;
-        a.denominator /= b.denominator;
+        a.numerator *= b.denominator;
+        a.denominator *= b.numerator;
     } else if (typeof b === 'number') {
-        a.numerator /= b;
+        a.denominator *= b;
     } else {
         return a.divide(new Fraction(b));
     }
     return a.normalize();
 }
 
-
 Fraction.prototype.equals = function(b)
 {
     if (!(b instanceof Fraction)) {