Make Range a native object type.

Still need to implement better semantics, but this is an 
important first step. It's much faster now too, which is good.

test/range/min.wren

@@ -0,0 +1,26 @@
+// Ordered range.
+IO.print((2..5).min) // expect: 2
+IO.print((3..3).min) // expect: 3
+IO.print((0..3).min) // expect: 0
+IO.print((-5..3).min) // expect: -5
+IO.print((-5..-2).min) // expect: -5
+
+// Backwards range.
+IO.print((5..2).min) // expect: 2
+IO.print((3..0).min) // expect: 0
+IO.print((3..-5).min) // expect: -5
+IO.print((-2..-5).min) // expect: -5
+
+// Exclusive ordered range.
+IO.print((2...5).min) // expect: 2
+IO.print((3...3).min) // expect: 2
+IO.print((0...3).min) // expect: 0
+IO.print((-5...3).min) // expect: -5
+IO.print((-5...-2).min) // expect: -5
+
+// Exclusive backwards range.
+// TODO: Is this what we want? "..." always means "subtract 1"?
+IO.print((5...2).min) // expect: 1
+IO.print((3...0).min) // expect: -1
+IO.print((3...-5).min) // expect: -6
+IO.print((-2...-5).min) // expect: -6