delay operator behavior is misleading

[mocheng]

When sliding one marble in source stream to right, the corresponding marble in result stream disappeared to the end. It looks that if one value is delayed after source completion, it is not passed on at all. This is not right.

And, the complete point is not delayed. This is not right either.

Perhaps the completion point of source stream should be moved ahead, so that there is enough space to show expected behavior.