Raise errors on accessors

I tried it in irb before I made the comment...`(200...300).last # => 300`, and `(200..300).last # => 300`, but you're right when I do `(200...300).each { |i| puts i }` and `(200..300).each { |i| puts i }` is different. Weird. Just realized that if I use `#last` on a range I need to call `#to_a` first - my bad.