* This automatically provides support for things like custom markers via
pointToLayer etc
* Also a significant bugfix for a bug that surfaced when using different marker
(like the CircleMarker) - and which took ~30m to track down. Bug was that the
call to zoom (or, more specifically, call to getBounds) occurred before
features were added to the map and getBounds for some objects (such as
circles) requires map to exit (so you can do a projection!)