* Update free-programming-books.md

The book-- <Realm of Racket> is not free.

* Update free-programming-books.md

Added a repo of Unix system programming in OCaml

* Update free-programming-books-pl.md

* Adding required blank line

* Removed trailing slash

* Fixing blank line again

* Add a book to JavaScript section (Spanish)

Spanish: free-programming-books-es.md

### JavaScript
- [JavaScript, ¡Inspírate!](https://github.com/UlisesGascon/javascript-inspirate)

* New order

New order

* Update free-programming-books.md

* Update free-programming-books.md

* Update free-programming-books.md

* Alphabetical order

* Adding books in Mathematics and Operating Systems

- Renamed book to A Byte of Python
- Fixed book ordering
- Changed link to https
- Fixed Python version (3.x)
- Added available formats

* Update broken links

* Small fix

* Update broken link

* Added The Internals of PostgreSQL

* Removed trailing slash

* Update free-programming-books.md

* Update free-programming-books.md

Added Jake VanderPlas's Python Data Science Handbook book to the Python list.

remove broken "windows phone" link

* Update with SystemVerilog FREE courses

SystemVerilog is IEEE1800 standard and most widely used Hardware Description language

* Update with SystemVerilog FREE course

Update with SystemVerilog (IEEE1800 standard and commonly used Hardware Description Language)

* Added material design tutorial

* Update free-courses-en.md

* Adding the API with Silex on GAE ebook, in pt_BR, PHP Section.

* Adding the API with Silex on GAE ebook, in pt_BR, PHP Section.

* Alphabetize the PHP ebooks in pt_BR.

* Add cocoa heads pt-BR podcast

* Update link anchor

* Add french book "Cours Ada 95 pour le programmeur C++", Q. Ochem

* Add Ada course in French from D. Feneuille

* Make changes to follow the guidelines

* Indicate a book is distributed as a ZIP file

added ScalaFiddle (s)

[Scala Exercises](https://www.scala-exercises.org/)

* [PythonToScala](https://wrobstory.gitbooks.io/python-to-scala/content/) - Rob Story

Original linked to a page whose download links were all broken. Linked instead to publisher's website, where the book can be downloaded for free.

* Remove problematic links

* Fix according to comments

* Formatting

* Update free-programming-playgrounds.md

* Update free-programming-playgrounds.md

* Update free-programming-playgrounds.md

* Update details for python course Programming for Everybody

El enlace del libro "El modelo relacional y el álgebra relacional" ya no funcionaba. Lo actualicé con un nuevo enlace que sí sirve.