Pass the error through on getOrElse

OK can we rename `error` to `err` everywhere else, too, then? Or just create a new PR to do the rename?

Also, you can pass in a 0-arity function where a 1-arity one is expected. From the caller's perspective, the parameter is NOT optional, it's just ignorable.

I.e.
```
var t = Try.success(5);
        t.getOrElse((err) => {
                return 6;
        });
```
works, even if `err` is required.