Instanced Mesh lags a frame behind in auto updateMode

[diarmidmackenzie]

If you enable "debug" mode in the physics examples, you can see that Instanced Mesh rendering lags a frame behind the physics engine's view of the world.

Possible this could be fixed by somehow making sure the instanced-mesh tick() (when we copy entity positions into the insance matrix array) happens afterthe physics tick(), but that might not be enough, and I think we can do better.

I'd like to find a way to move this copy into the render pipeline, after THREE.js has done a full update of all matrices, but before actually doing the rendering. Can probably use techniques similar to [this].(https://github.com/diarmidmackenzie/aframe-multi-camera#add-render-call)

Benefits of this would be 2-fold:

• no need to update matrices other than the updates THREE.js already does.
• matrix data would always be up-to-date at the point of copying.

Even in manual update mode, we should queue up the upates, and actually perfrom them at this later stage. That would avoaid the need to do additional matrix updates over & above those already done per-frame by THREE.js, so we could also solve #12 at the same time.

[diarmidmackenzie]

Fixed by #25