Bring back update() on tweeners please (or an equivalent)

[technobaboo]

Back in tween v1.0.1 I could do

if let Some(height) = rez_height_tweener.update(info.delta) {
	let _ = self.lines.set_position(None, [0.0, height, 0.0]);
} else if let Some(scale) = rez_scale_tweener.update(info.delta) {
	let _ = self.lines.set_scale(None, [scale; 3]);
} else {
	self.state = State::Idle
}

to run tweens in sequence extremely easily, but now with the changes I have to do

if !rez_height_tweener.is_finished() {
	let height = rez_height_tweener.move_by(info.delta);
	let _ = self.lines.set_position(None, [0.0, height, 0.0]);
} else if !rez_scale_tweener.is_finished() {
	let scale = rez_scale_tweener.move_by(info.delta);
	let _ = self.lines.set_scale(None, [scale; 3]);
} else {
	self.state = State::Idle
}

It's not that bad of an inconvenience I guess but it was just so nice to use Options for this for my workflow