Fixed non-working links (#3508)

free-programming-books.md

@@ -2237,7 +2237,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Test-Driven Web Development with Python](http://www.obeythetestinggoat.com/pages/book.html) - Harry Percival (3.3 - 3.x)
 * [Text Processing in Python](http://gnosis.cx/TPiP/) - David Mertz (2.3 - 2.x)
 * [The Coder's Apprentice: Learning Programming with Python 3](http://www.spronck.net/pythonbook/) - Pieter Spronck (PDF) (3.x)
-* [The Definitive Guide to Jython, Python for the Java Platform](http://www.jython.org/jythonbook/en/1.0) - Josh Juneau, Jim Baker, Victor Ng, Leo Soto, Frank Wierzbicki (2.5)
+* [The Definitive Guide to Jython, Python for the Java Platform](https://jython.readthedocs.io/en/latest/) - Josh Juneau, Jim Baker, Victor Ng, Leo Soto, Frank Wierzbicki (2.5)
 * [The Little Book of Python Anti-Patterns](http://docs.quantifiedcode.com/python-anti-patterns/) ([Source](https://github.com/quantifiedcode/python-anti-patterns))
 * [The Programming Historian](http://niche-canada.org/research/niche-digital-infrastructure-project/the-programming-historian/) - William J. Turkel, Adam Crymble and Alan MacEachern
 * [The Python Ecosystem: An Introduction](http://mirnazim.org/writings/python-ecosystem-introduction/)
@@ -2346,7 +2346,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [I Love Ruby](https://i-love-ruby.gitlab.io)
 * [Introduction to Programming with Ruby](https://launchschool.com/books/ruby) - Launch School
 * [Just Enough Ruby to Get By](http://jasonkim.ca/projects/just_enough_ruby_to_get_by/)
-* [Learn Ruby First](https://www.learnruby.today) - Frederick John
+* [Learn Ruby First](https://essenceofchaos.gitbooks.io/learn-ruby-first/content/) - Frederick John
 * [Learn Ruby the Hard Way](http://learnrubythehardway.org/book/) - Zed Shaw
 * [Learn to Program](http://pine.fm/LearnToProgram/) - Chris Pine
 * [Mr. Neighborly's Humble Little Ruby Book](http://www.humblelittlerubybook.com)
@@ -2379,7 +2379,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Building REST APIs with Rails](http://apionrails.icalialabs.com/book)
 * [Kestrels, Quirky Birds, and Hopeless Egocentricity](https://leanpub.com/combinators/read) - Reg Braithwaite
 * [Learn Ruby on Rails as You Modify a Craigslist Clone](http://www.thinkful.com/learn/ruby-on-rails-tutorial/)
-* [Objects on Rails](http://objectsonrails.com)
+* [Objects on Rails](https://web.archive.org/web/20190319201525/http://objectsonrails.com/) - Avdi Grimm
 * [Rails Girls Guides](http://guides.railsgirls.com)
 * [Ruby on Rails 3.2 - Step by Step](http://www.xyzpub.com/en/ruby-on-rails/3.2/)
 * [Ruby on Rails 4.0 Guide](http://www.xyzpub.com/en/ruby-on-rails/4.0/)
@@ -2396,7 +2396,7 @@ Kerridge (PDF) (email address *requested*, not required)
 ### Rust
 
 * [Rust by Example](https://doc.rust-lang.org/stable/rust-by-example/)
-* [Rust for Rubyists](http://www.rustforrubyists.com/book/index.html)
+* [Rust for Rubyists](https://web.archive.org/web/20190520171322/http://www.rustforrubyists.com/book/index.html) - Steve Klabnik
 * [The Rust Programming Language](http://doc.rust-lang.org/book/)
 * [The Rustonomicon](https://doc.rust-lang.org/nomicon/)
 * [Why Rust?](http://www.oreilly.com/programming/free/files/why-rust.pdf) (PDF)
@@ -2412,7 +2412,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 * [A Scala Tutorial for Java programmers](https://docs.scala-lang.org/tutorials/scala-for-java-programmers.html) (PDF)
 * [Advanced Scala with Cats](http://underscore.io/books/advanced-scala/) - Noel Welsh and Dave Gurnell (PDF, HTML, EPUB) (email address *requested*, not required)
-* [Another tour of Scala](http://naildrivin5.com/scalatour/)
+* [Another tour of Scala](https://web.archive.org/web/20190629103826/http://naildrivin5.com/scalatour/) - David Copeland
 * [Creative Scala](http://underscore.io/books/creative-scala/) - Noel Welsh and Dave Gurnell (PDF, HTML, EPUB) (email address *requested*, not required)
 * [EAI Patterns with Actor Model](https://github.com/alexanderfefelov/eai-patterns-with-actor-model) - Vaughn Vernon
 * [Effective Scala](https://twitter.github.io/effectivescala/)