title: speedup leaflet map refresh after zoom change
body: <p>I want the "old" map to be erased quicker after a zoom change.  For example: at zoom level 16, I can see a city name, but when I zoom into zoom17... that city name is not in view anymore... which works... but there is always a little delay before the old map data goes away.  </p>
  
  <p>I've seen how to change the zoom animation speed... but not this specific thing.  I think it might have to do with the fact that I'm working with a transparent map...</p>
  
  <p>It feels like a setTimeout function to erase the 'old' map at the previous zoom level. I just want to speed it up.</p>
  
  <p>EDIT:  I looked through the code and found this function: _onZoomTransitionEnd
  and saw that it was attached to a timeout, but I changed the timeout time and it didn't seem to do anything.</p>
  
  <p>EDIT#2:  Upon further investigation... I'm getting this problem in leaflet .7.7.  but not the most recent version of leaflet (1.0.1 and beta).  HOWEVER, the most recent version doesn't load tiles during a panning operation... it waits until the pan is done until loading tiles.  Leaflet 77 doesn't do this, it loads 'on the fly'.  So I guess I have two options:    Use the map with a delayed zoom-delete of the previous layer.... or use a map with nice quick zoom response... but a delayed response on rendering new tiles when panning to different places on the map.  I'm thinking option #1 is probably the least disruptive.</p>
  
  <p>EDIT #3:  And now everything is working on Leaflet 1.0.1   so maybe I was just going crazy.  Once again, thankyou to the people making leaflet... you are amazing.</p>