Use a general transformation type for certain operations such as ray-object queries

[`toi_with_ray`](https://www.ncollide.org/rustdoc/ncollide3d/query/trait.RayCast.html#method.toi_with_ray) takes an isometry which is the transformation to apply to the object. Unfortunately, isometrys do not involve scaling, so if I wanted to query rays against a objects of various sizes, I would have to do various transformations to either the ray or the object. I think it would be better to use a general transformation type for this sort of thing that did incorporate scaling.