Fix #2. Finish implementing Range.

Covers error and edge cases and fully tested now.

test/range/to.wren

@@ -12,14 +12,14 @@ IO.print((3..-5).to) // expect: -5
 IO.print((-2..-5).to) // expect: -5
 
 // Exclusive ordered range.
-IO.print((2...5).to) // expect: 4
-IO.print((3...3).to) // expect: 2
-IO.print((0...3).to) // expect: 2
-IO.print((-5...3).to) // expect: 2
-IO.print((-5...-2).to) // expect: -3
+IO.print((2...5).to) // expect: 5
+IO.print((3...3).to) // expect: 3
+IO.print((0...3).to) // expect: 3
+IO.print((-5...3).to) // expect: 3
+IO.print((-5...-2).to) // expect: -2
 
 // Exclusive backwards range.
-IO.print((5...2).to) // expect: 1
-IO.print((3...0).to) // expect: -1
-IO.print((3...-5).to) // expect: -6
-IO.print((-2...-5).to) // expect: -6
+IO.print((5...2).to) // expect: 2
+IO.print((3...0).to) // expect: 0
+IO.print((3...-5).to) // expect: -5
+IO.print((-2...-5).to) // expect: -5