hide notifications after few seconds

[crackcomm]

First of all - thank you for this genius tool.

I found only single thing that I could improve but I've never used elm so I can't really submit a patch now.
During edition of artifacts, I have a pretty long notifications list because I am too lazy to click X every time.
It would seem useful but there is already a better tool inside artifact - an entire change history.

If it would disappear after few seconds (or use "toasts" instead) it would greatly improve usability (at least for me). Thank you.

[vitiral]

I had meant to have this behavior but just never got around to implementing it.

I would also like the notifications "float" instead of cause the screen to move.