I'm sure @tpetricek can confirm his book is not free

the Lua Programming Gems book is not freely available (apart from the second chapter and notes for some other chapters), and is not a general guide to the language; the first edition of Programming in Lua, however, *is* freely available, and *is* a guide for learning the language in general.

* Added a new Scala book

"Functional programming for mortals" is a very good book about Scala and it is free to read on the web.

* Removed the '*' at the end

* Added Thinking in HTML book (free eBook) to HTML section

* Update free-programming-books.md

* Update free-programming-books.md

* Guia JavaScript

* Guia JavaScript da Mozilla

* added back a required space

* Update free-programming-books-id.md

* Update free-programming-books-id.md

* Update free-programming-books-id.md

* Added "Julia language: a concise tutorial"

https://www.gitbook.com/book/sylvaticus/julia-language-a-concise-tutorial

* Removed PDF tag and added the second blank line

* Update free-podcasts-screencasts-en.md

added 2 new Podcasts.

* Remove trailing slash in URL

* This book doesn't seem to have anything to do with Mathematica.

* Added a free/open book on Algorithms in Python

Linked to the github repo, but it links to a PDF download from there.

* added author name

* implement #2357

* Jane Roe is an awesome writer

also, her website is secure!

* add two books in `-zh` list in `Python` section

* https -> http on explore-python link

* Added CodeIgniter Framework

* Added CodeIgniter Framework

* Update free-programming-books-ru.md

* the old site has not update so this is the new one

* remove trailing slash from url to satisfy travis

* Update free-programming-books.md

* Update free-programming-books.md

* Fix a broken link

* Fix broken link

* Adding new Python book

* Adding Python 3 Book

* correct markdown syntax

(I think we even have some free books *about* markdown!)

* Updated broken C# link 

The link for "Data Structures and Algorithms with Object-Oriented Design Patterns" under C# was broken. I updated it so it goes to the correct pdf file.

* change to Wayback link from discussion

https://web.archive.org/web/20161220072449/http://www.brpreiss.com/books/opus6/

Joy of Elixir is an in-progress book to teach newbies Elixir that I'm writing.

Thanks to @ckhrysze for the prompting to add the book to this list.

* Added Pyfiddle (https://pyfiddle.io/)

* satisfy Travis

* 添加正则表达教程

* Update free-programming-books-zh.md

* Python books: Formatting for multiple editions

* added ref to issue 2353

Add Free Competitive Programmers Handbook link to author's website. PDF available.

Include downloads link for a zipped html and pdf versions of a C book.

* Add Go playground

* Fix Travis build

* Remove broken link

* removed empty swift category

* Removed broken links

* Remove broken link

* removed empty swift category

* Python books: Formatting for multiple editions

* added ref to issue 2353

* .

* 1. Domain name http://reactjs.cn was sold and it is not related to react js for now. So I change it to another available site.

2. Tweak React to React.js

* fix ordering

* fix #2500

* removed empty android heading

Thanks for the contribution!
* add three book in free-programming-books-zh.md `Python` section

* order of adjustment

* remove the book in english and add author

* Add: The Official Raspberry Pi Project Book

* Add: The Official Raspberry Pi Project Book + Format