adding in the ability for overlays layers to be forced above all others....

... Used for rendering labels overlay on top of all other layers

this is very useful when wanting to render a separate labels layer on top of things like polygons. You can now add .forcetotop=true as a layer property and it work.

Leaflet 1.0 should support this without the hack see:
http://stackoverflow.com/questions/19939607/overlay-below-tiles-in-leaflet-js