Added Cube example

README.md

@@ -2,6 +2,7 @@
 
 ### Examples
 
+[![cube.png](http://github.com/mrdoob/three.js/raw/master/examples/geometry/cube.png)](http://mrdoob.com/lab/javascript/three/geometry/cube.html)
 [![random.png](http://github.com/mrdoob/three.js/raw/master/examples/particles/random.png)](http://mrdoob.com/lab/javascript/three/particles/random.html)
 [![waves.png](http://github.com/mrdoob/three.js/raw/master/examples/particles/waves.png)](http://mrdoob.com/lab/javascript/three/particles/waves.html)
 [![floor.png](http://github.com/mrdoob/three.js/raw/master/examples/particles/floor.png)](http://mrdoob.com/lab/javascript/three/particles/floor.html)