Updated "Dive Into Python" links (#3420)

The "official" Dive Into Python links no longer go to the books. There is no great authoritative link to use since Mark Pilgrim left the internet, but these are returned high in Google results and appear to load really quickly.

free-programming-books.md

@@ -2130,8 +2130,8 @@ Kerridge (PDF) (email address *requested*, not required)
 * [CodeCademy Python](https://www.codecademy.com/learn/python)
 * [Composing Programs](http://composingprograms.com) (3.x)
 * [Data Structures and Algorithms in Python](https://web.archive.org/web/20161016153130/http://www.brpreiss.com/books/opus7/html/book.html) - B. R. Preiss (PDF)
-* [Dive into Python 3](http://getpython3.com/diveintopython3/) - Mark Pilgrim (3.0)
+* [Dive into Python 3](https://diveintopython3.problemsolving.io) - Mark Pilgrim (3.0)
-  * [Dive into Python](http://www.diveintopython.net) - Mark Pilgrim (2.3)
+  * [Dive into Python](https://linux.die.net/diveintopython/html/toc/index.html) - Mark Pilgrim (2.3)
 * [From Python to NumPy](http://www.labri.fr/perso/nrougier/from-python-to-numpy/)
 * [Full Stack Python](http://www.fullstackpython.com)
 * [Functional Programming in Python](http://www.oreilly.com/programming/free/functional-programming-python.csp) (email address *requested*, not required)