Torus implemented

-ka 0.2 0.2 0.2 -kd 0.7 0.7 0.7 -ks 0.7 0.2 0.2 -pl 4.0 0.0 2.0 0.7 0.1
0.1 -pl 0.0 4.0 2.0 0.4 0.5 0.9 -pl -4.0 -4.0 1.0 0.4 0.8 0.5 -pl 0.0
0.0 1.0 0.4 0.5 0.9 -sp 20.0 -tor 5 10

returns http://i.imgur.com/Uh6dtYz.png

The current command line argument is "-tor innerradius outerradius",
however the last two arguments don't actually do anything in the current
code, since I just hardcoded the size in the function. I've left it in
case it proves useful to actually specify the size. Also don't try to
create a render without the ambient coefficient, it looks weird with
only one light.