Update pythreejs.py
Update pythreejs.py

Added cube geometry
Joel-Venzke/pythreejs,Joel-Venzke/pythreejs,jasongrout/pythreejs,farizrahmat/pythreejs,nlooije/pythreejs,nlooije/pythreejs,nlooije/pythreejs,jasongrout/pythreejs,farizrahmat/pythreejs