first npm install in root AND app/ then run gulp watch and eveything should be fine
you can add a update(dt, stage) function to your THREE.Object3D Instances that will automatically be called when added to the scene, or any children, childrens children ... of the scene. Arguments it will receive are dt, deltaTime since the last call and stage which will have stuff like the renderer, scene and camera.
Disable the update (not rendering) of an object and its children by setting Object.active = false