Merge branch 'natural_language' of github.com:Haskmell/free-programming-books into Haskmell-natural_language

Conflicts:
	free-programming-books.md

fixed Perl 6 link in contents

fix url

Add Flask tutorail

Added 'Haskell and Yesod'

Added Scala School by Twitter

adding two link for "Sage", the mathematical software system

Update free-programming-books.md

Updated links to Dive Into HTML5

Added Git internals

Added link to "The Bastards Book of Ruby"

Added link to Eijkhout's Intro to HPC

Add Jan Newmarch's "Network Programming in Go"

1. Changed the link to the community-maintained web version of the book.

2. Added a link to a PDF version of Dive Into HTML5.

Both of these resources have been updated and enhanced and build upon the original work by Mark Pilgrim.

Added some books

Icon book (and heading), Joe Armstrong's thesis, Small Memory Software, Purely Functional Data Structures, OpenGL Insights

Update free-programming-books.md

Added an entry for the processing programming language.

Removed "Ruby Best Practices"

This is neither a book nor free.

Updated Mixu's Node Book since the author has moved it

Fix typo "Getting started with Grails"