Blend specular color with reflected color
Add cross product operation to Vector3
Add Planes
Add operator<< overloads for Vector3, Ray, and Color
Add operator<< overload for Object
Add object_plane.cc to the build
Add a plane to the scene
Shift the plane down (I think)
Shift scene objects around to try to see a plane...
Return Vector3::Zero for normal if point is not on surface of plane