Update colab example notebook

[chrisadas]

As of today, the example colab notebook could not execute successfully.

https://colab.research.google.com/drive/1b7Uo9Ic1UltWvC2S7-qqix5WUL-P86xD

I updated the dependent packages to what I think are reasonable versions for the present.

https://colab.research.google.com/drive/1d4u2zXwHX5Y1UdXugksBTfDeNdVX82Dq

Original lines are commented, and some remarks added as comments as well. Everything except the last 2 cells can be executed successfully. I don't know how to fix the last bit.