assert and test changes

examples/demo.monkey

@@ -40,4 +40,4 @@ let map = fn(arr, f) {
 };
 
 let numbers = [1, 1 + 1, 4 - 1, 2 * 2, 2 + 3, 12 / 2];
-//map(numbers, fibonacci);
+map(numbers, fibonacci);

examples/fact.monkey

@@ -5,4 +5,4 @@ let fact = fn(n) {
   return n * fact(n - 1)
 }
 
-print(fact(5)
+assert(fact(5) == 120, "fact(5) != 120")