[challenge] Bounded types

[Adam D. Ruppe]

> I think scope(success) is an overkill here.

Yeah. It is in my brain due to writing a lot of database code with it:

db.query("START TRANSACTION");
scope(success) db.query("COMMIT");
scope(failure) db.query("ROLLBACK");


> Well done otherwise, looking forward for final version!

Thanks.

For future direction, I don't think the Type argument is actually needed to the
Bounded struct. It could determine it from the bounds.

So Bounded!(0, 255) it knows could be a ubyte, but Bounded!('A', 'Z') is a char.

Maybe the type param can be moved to the end, as an optional parameter. In most
cases, it should be able to figure it out on its own.