Align libigl barycentric coordinates to compas.

[petrasvestartas]

Fix to the bug described here: #34

[yiqiaowang-arch]

Hi @petrasvestartas , thank you very much for the work!

I found several problems here:

1. the output of intersection_ray_mesh still doesn't match that of compas.geometry.barycentric_coordinates (see Clearer documentation for intersection_ray_mesh #34 (comment));
2. the typehint in the docstring is incorrect (also see Clearer documentation for intersection_ray_mesh #34 (comment));
3. (maybe not directly related to this repo but) the compas.geometry.intersection_ray_mesh's docstring labels the second and third outputs as u, which is also incorrect (see https://github.com/compas-dev/compas/blob/dc6f2deee7a8eb504be20798e281fc0318ba37da/src/compas/geometry/intersections.py#L746).