Make notebooks runnable in google colab

[JochenSiegWork]

Make it possible for users to try out Molpipeline directly in google colab.

• Add Colab tag/Link to our notebooks and readme
• Add check on beginning of notebooks to install Molpipeline automatically on colab
  • See https://stackoverflow.com/questions/53581278/test-if-notebook-is-running-on-google-colab

See also https://colab.research.google.com/github/googlecolab/colabtools/blob/master/notebooks/colab-github-demo.ipynb

Chemprop has some example code how to install the package on colab https://chemprop.readthedocs.io/en/latest/training_regression_multicomponent.html