Integration with ipyleaflet

[davidbrochart]

I want to get this plugin into IPyLeaflet. It works well except that when there are several views of a map, the handlers are not properly synced. When a Polygon view gets transformed, all the views receive a setLatLngs([...]), and I call transform.reset() after that as explained in the documentation.
Here is a binder if you want to see what is going on:
https://mybinder.org/v2/gh/davidbrochart/ipyleaflet/transform?filepath=examples%2FTransform.ipynb