/closes #553

this pr is indeed for increasing the responsiveness of plotting time slider.

during testing i found that the slider itself is not an issue but the computation was , to resolve this i adopted following approach -
1 use the down sample on initial slider event (low resolution but not that low)
2 increasing slider responsiveness (asserted by consoling the time taken)
3 when the slider stops updating that down sample to full resolution
4 i see that whenever we fires two events one after another both are getting processed (since python is single threaded on main gui) but what if we fires many events ?

• current approach handle this as handling each event
• in this implementation i try to cancel that extra events it works when _update is fast enough and/or is broken into smaller chunks (here we check between each attribute update)