Removed book that is no longer free

Added several books to Mathematics and one to R

Added books to Datamining and Machine Learning sections

Added Network Science book to Theoretical Computer Science section

I had believed that this book was free, I think at some point it was,
but following a comment from johand, it is clear that this is no longer
the case, and a result, not suitable for this list.

Added 6 statistics books to Mathematics section and one book to the R section

I'm not sure exactly what section this belongs in; it seems to be influenced by several fields.  If someone else knows a better section, I'd be happy to move it.

Added Introduction to Data Science and A First Course in Linear Algebra

Added complete titles as part of 'The Architecture of Open Source Applications'.  
Moved entry to be with 'The Performance of Open Source Applications' which is in the same series.

Creating AngularJS sub-section

Moved "AngularJS in 60 Minutes" to new sub-section Angular.js

Lisp pdf link

Added COBOL section with 2 PDFs

Some spanish books about javacript and css

add Backbone.js API Link, README Item

[COBOL] (#cobol)  works but [COBOL] (#COBOL) doesn't

3 more spanish books (mostly translations from english books)

Update free-programming-books-pt_BR.md

Python para desenvolvedores

updating readme

Update free-programming-books-pt_BR.md

Introducao ao Shell Script - Aurelio ( Verde ) 
Tutorial de Ruby - Eustaquio Rangel

added Learn to Program by Chris Pine (under Ruby)

openlibra

Added Data-Oriented design free eBook

This reverts commit dd0b69d0.

Update free-programming-books.md

css book