Fix #2. Finish implementing Range.

Covers error and edge cases and fully tested now.

test/range/max.wren

@@ -12,11 +12,11 @@ IO.print((3..-5).max) // expect: 3
 IO.print((-2..-5).max) // expect: -2
 
 // Exclusive ordered range.
-IO.print((2...5).max) // expect: 4
+IO.print((2...5).max) // expect: 5
 IO.print((3...3).max) // expect: 3
-IO.print((0...3).max) // expect: 2
-IO.print((-5...3).max) // expect: 2
-IO.print((-5...-2).max) // expect: -3
+IO.print((0...3).max) // expect: 3
+IO.print((-5...3).max) // expect: 3
+IO.print((-5...-2).max) // expect: -2
 
 // Exclusive backwards range.
 IO.print((5...2).max) // expect: 5