Remove large file
There is a very large file in the repository: https://git.embl.de/grp-bio-it/image-analysis-with-python/blob/master/session-7/extracted_features.csv.zip. We need to remove it from history in order to also put this repository on github to serve the notebooks with binder. This file is not used inside the session 7 notebook, so it should be fine to remove it.
If we want to keep the file somehow, we could create some legacy branch first.