both catergories are the same. I also put the title of Lisa Watts's book in spanish (as the translations version has)

Update free-programming-books.md

added Twitter share button

I couldn't add a Facebook share button because I don't have an account but here is the link if someone else wants to add it:

https://developers.facebook.com/docs/plugins/like-button/

Initial removal of english books from chinese(zh) books list.

Some changes

- Removed "A Course in Machine Learning". There were 2 same links in the
list. One of them kept which is originally belong the author
- Added 1 Android and 2 Powershell books

Add a coffeescript book

Adding Arduino

Added "A Course in Machine Learning"

Added two Tcl books

Add a ruby on rails metaprogramming book

Added "Kestrels, Quirky Birds, and Hopeless Egocentricity" under the Ruby on Rails.

Add Explore Flask book (crowdfunded)

Algorithms - Berkeley link doesn't require signup

Add french book "Calcul mathématique avec Sage", collectif

Removal decisions were made comparing it with the english(en) books list; itens with the exact same link were removed.
Further removal may need a more careful consideration, since for some reason these book's titles were translated to chinese in the *zh* list.
Added 3 chinese(zh) books.

remove broken macruby link

Formatting fixes:

Added empty line before heading "Information Retrieval" to fix html output.
Untabified one line in Python section.

Gradle Section + Building and Testing with Gradle

Added a Gradle Section and the book Building and Testing with Gradle

Fixing and Adding various links

une introduction aux makefile