Adicionado Grunt

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

Adicionado Grunt
[en] Adding Operating System Book
Merge pull request #821 from esparta/master

[en] Adding Operating System Book
Update free-programming-books-zh.md
Merge pull request #822 from yangboz/patch-1

Update free-programming-books-zh.md
Added Speaking JavaScript online book from Dr. Axel Rauschmayer
Merge pull request #823 from thebouv/master

Added Speaking JavaScript online book from Dr. Axel Rauschmayer
[es] Adding a security book
Merge pull request #824 from esparta/master

[en] Adding a security book
added speaking js
Merge pull request #825 from orzogen/master

added speaking js
Remove duplicate (Speaking JS)
Fixed markdown syntax
Added books in czech language
Merge pull request #826 from grogy/fix-markdown-syntax

Fixed markdown syntax
Merge pull request #827 from grogy/czech-books

Added books in czech language
add a software architecture book
Merge pull request #828 from alrz/patch-1

add a software architecture book
Fixes #819