Merge pull request #28 from alexlarsson/master

Fix graphene_matrix_transform_sphere
Fix graphene_simd4x4f_init_look_at

I don't understand why this should ever be transposed, and
with this fix gthree_object_look_at() in Gthree finally works.

That said, this breaks the tests, so either Gthree is wrong (but i
don't think so) or the tests need fixing.