Textures with transparency are white if a light is not added to scene

If a light isn't in a scene, the transparent parts of textures become white.

http://scotland.proximity.on.ca/asalga/gladius/gladius_transparency_issue.png

The workaround is to create a dummy light

``` JavaScript
new engine.graphics.component.Light({
  type: "point",
  method: "dynamic",
  diffuse: [0, 0, 0 ],
  specular: [0, 0, 0 ],
  intensity: 100,
  distance: 0
 })
```
