Create CONTRIBUTING.md

This will allow new github users to see this document when they open a new issue??
Update CONTRIBUTING.md

removing question marks and uppercase title.
add index to contributing
use relative path to create the index

This seems to be working so, I'm going to leave it like this
Merge pull request #1 from gero3/patch-6

Patch 6
make sure the index link als works
Update CONTRIBUTING.md
Update CONTRIBUTING.md
update Contributing according to @mrdoob
Event system implementation for deallocating geometries and textures.
It's hard to test because, I think, chrome is now automatically deallocating stuff on it's own
@alteredq I've done a combined deallocateGeometry and some things here and there would need to be refactored but... what do you think?
Update CONTRIBUTING.md
Update CONTRIBUTING.md
Update CONTRIBUTING.md
implemented Box3.transform, tested.  Removed Box3/Box3.scale as it doesn't work in the general case.  move tests to tests/math from tests/core to replace move of tested source files.
rename Ray.transformSelf -> Ray.transform (simplier name more consistent with rest of library.)
add Plane.transform + Sphere.transform, no tests yet.
finish Sphere unit test coverage (it was previously incomplete) and fix uncovered errors.
update the contributing file for root usage
complete Plane unit tests.  fix bugs with Plane.translate and Plane.transform.
Matrix4.makeTranslation and Matrix4.makeScale now take Vector3 instead of thee scalars per #2780