text: Title: Standalone HTML representation of animation not loading
  Body: I've tried running the hydrogen example notebook through nbconvert to get a "static" representation. The produced html file will generally load, but the plot will not. 
  Browser console (same error in firefox)
  [k3d.log](https://github.com/K3D-tools/K3D-jupyter/files/6765093/k3d.log)
  I've added the converted html too (zipped since GitHub doesn't allow html attachments:
  [k3d.html.zip](https://github.com/K3D-tools/K3D-jupyter/files/6765102/k3d.html.zip)
  
  