Kai
Allow setting the tqdm.disable option from the environment variables. The default value of `False` is unchanged, as is the expected behavior with `None`. Resolves issues laid out it #619 #614...
**The textbook version available in this repository is version 4.0 - whereas the solutions correspond to version 4.1. This inconsistency arose simply because a softcopy of version 4.1 seems unavailable....
The HTML title of the page is currently `Music` / `Song name - Artist name`. This seems okay at the outset, but it could be improved. Browsers remember the title...