Support Google Colab for authoring workflow

[salikh]

Currently the authoring workflow assumes Jupyter notebooks, but it would be nice to support authoring in Colab, as it allows for better collaboration of multiple people and quick turn around.

Specifiically, the following is necessary:

• Ability of the build system to download notebooks from Colab / Google Drive
• Ability to install prog_edu_assistant_tools package from PyPI (Publish prog_edu_assistant_tools package to PyPI #34)