text: Title: Expose material property 'shininess' for objects
  Body: I have a use-case where I would need some meshes to appear shiny whereas others should not. Setting plot.lighting = 0 achieves the latter effect, but then all objects in the scene are affected. I believe this could be controlled individually for each object if the material shininess property, e.g. for a Surface object,  https://github.com/K3D-tools/K3D-jupyter/blob/46bec8581e213351aa5df621c1825b95c732486b/js/src/providers/threejs/objects/Surface.js#L36
  would be exposed and not hard-coded.
  
  I believe exposing this would also to some degree address the comment raised previously in #51.