A wild revision appeared! (0.7.2-r1)

Hello everyone!

Here is a minor revision of the book, thanks to Nivanchenko on GitHub for highlighting a glaring mistake on the distance formulas and fixing it too!

This release sees more under-the-hood changes that will probably help in the future.

For now, it's just what I think is an important fix and a copyright year update.

Thank you all for your attention!

Penaz