Added Italian and Portuguese translations + Updated version. (#4595)

* Added Portuguese and Italian Translations.

Added Portuguese and Italian Translations of the book Python For Everybody by Dr. Charles Russell Severance

* Update free-programming-books.md

Updated the link to the latest edition.

* Update free-programming-books.md

Updated edition for the book with author and links in three places.

* Update free-programming-books.md

Added Think DSP - Digital Signal Processing in Python.

* Update free-programming-books.md

Added Think Data Structures: Algorithms and Information Retrieval in Java.

* Update free-programming-books.md

Added two new books;
Think C++: How To Think Like a Computer Scientist
Modeling and Simulation in Python

* Minor changes to adhere to Contributing.md

Thanks to @kashirash
Suggested edits to pass travis-ci and respecting markdown formatting.

free-programming-books-pt_PT.md

@@ -5,6 +5,7 @@
 * [Haskell](#haskell)
 * [LaTeX](#latex)
 * [Prolog](#prolog)
+* [Python](#python)
 
 
 ### C/C++
@@ -32,3 +33,8 @@
 ### Prolog
 
 * [Lógica Computacional (com Prolog)](http://www4.di.uminho.pt/~mjf/pub/LC-Prolog.pdf) - Maria João Frade (PDF)
+
+
+### Python
+
+* [Python Para Todos: Explorando Dados com Python 3](http://do1.dr-chuck.com/pythonlearn/PT_br/pythonlearn.pdf) - Dr. Charles Russell Severance (PDF) [(EPUB)](http://do1.dr-chuck.com/pythonlearn/PT_br/pythonlearn.epub)