tuned ray-triangle intersection, now there are three algorithms to choose from:
Plucker, Barycentric and Barycentric with preprocessing (Wald)
methods in Vector and Shape (and derivates) made const
new C++ demo: realtime_dragon.cc
class Container moved to its own source file (from kdtree.*)
new directory for models and Makefile which downloads and prepares them
fixed python module path in some forgotten demos
ShapeList moved to scene.h