handle: A Range that handles an Exception

When a Exception occurs inside a range chaining the whole chain dies usually. The Handle range fixes that, as it catches a defined exception and calls an user defined handler on it.
Also, you should probably have an explicit test with something like `FrontThrow` as well. I'm not sure whether `splitter` throws on `front` or `popFront` (probably `popFront`), but regardless of which it does, it could change in the future. So, you'll want an explicit test for a range that throws on `front`.

You should probably also have a test with an infinite range. If you did, you'd have caught your use of `empty` with parens in `Handler`, since it wouldn't have compiled.