* Update "How to Think Like a Computer Scientist: Learning with Python" and "Think Python"

* "How to Think Like a Computer Scientist: Learning with Python":
  * Fix obsolete links: update URI and use HTTPS.
  * Add more editions to the title.
* "Think Python":
  * It diverges from "How to Think Like a Computer Scientist: Learning with Python" with many changes. So Allen B. Downey is the single author of this title.
  * Move it up one level and add the first edition.

* Update "How to Think Like a Computer Scientist: Learning with Python" and "Think Python"

* Rearrange the links to meet the Formatting Guidelines.