#311 SceneJS_Display._ambientColor now supports an alpha value

- also removed duplicate code in flags.js,
- and rebuilt api,
- and ammended .gitignore to exlcude node_modules.

With the new build it is not possible to set the canvas to have a transparent background like so: `scene._engine.display._ambientColor = [0,0,0,0]`

Running node build.js seemed to affect more files that I anticipated, wasn't sure how best to deal with that.