Correctly finish scroll animation when using page keys

[xPaw]

Fixes #1022.

When .finish() is called on an element, the currently-running animation and all queued animations (if any) immediately stop and their CSS properties set to their target values. All queued animations are removed.

[xPaw]

This if should have been lower by the way, so it doesn't really work anyway.

[astorije]

Haven't tested but looks fine to me.
@YaManicKill, let me know if you want to test it or not and if not I'll do that later, so at least one of us tests it.

[AlMcKinlay]

@astorije I'm not bothered, I just want one of us to test it. If you get to it first, feel free. I'll let you know if I manage to get some time to do it this evening or not.

[AlMcKinlay]

So, it does owrk, but it goes incredibly quickly. It's probably better than what we have now, but definitely not ideal.

[astorije]

Anything you think can be improved, @xPaw?

[xPaw]

Initially I wanted to get jQuery's animation state, so I could get final scrollTop target, stop the animation and start a new one with adjusted scrollTop, but there jQuery provides no way of doing that. I could be storing scroll data myself to re-use, but I don't know if it's worth it?

[astorije]

I could be storing scroll data myself to re-use, but I don't know if it's worth it?

It's probably worth a try, but if this PR already improves things, that's a win IMO. I'm going to merge this as-is, and feel free to attempt something better (but probably more experimental) for a future improvement.

Either way, thanks for that!