Updates polyline measurements on edit

[olzraiti]

Currently if you edit a polyline, the measurements don't update until you stop editing. The polygon edges update during editing, so this PR makes the plugin more consistent since the polyline behaves more like polygons.

You can reproduce the current behaviour by:

1. going to the demo page https://prominentedge.com/leaflet-measure-path/
2. Making the polyline editable by entering to console map._layers[39].enableEdit()
3. Dragging the polyline corners doesn't update the polyline measurements

EDIT: Polygon doesn't update actually properly when editing, but rectangle does. I'll apply the fix for polygon also.
EDIT2: Polygon fixed now also

[juliogontor]

It works very well