ConcaveHull Algorithm

One horrible dog of a ConcaveHull algorithm

Includes triangulation and polygon merging.

Signed-off-by: James Piggles <jack@homeflow.co.uk>
Merge branch 'master' of https://github.com/homeflow/Leaflet.draw

Signed-off-by: James Piggles <jack@homeflow.co.uk>

Conflicts:
	examples/basic.html