Update free-programming-books.md

Fixed typo.
Updated JavaScript list

Added Google JavaScript Style Guide. Also alphabetized the JavaScript list.
Merge pull request #818 from sjmcallister/master

Update free-programming-books.md
Merge pull request #813 from virendrachandak/patch-1

Updated JavaScript list + Google Javascript
Adicionado Grunt

Adicionado artigo sobre Grunt
Merge pull request #820 from wbecher/master

Adicionado Grunt