Add a section for official standards; add POSIX.

Under the Language Agnostic section, I've added a heading for standards documents, and started by adding the POSIX standard, which links to some instructions I've posted on how to access it without paying. I actually have a number of these, if you think it's the type of thing that would be useful on this list?
Corrected typo in index
Created initial Hungarian list
Merge pull request #550 from vicziani/hungarian

Created initial Hungarian list
Merge pull request #551 from vicziani/typos

Corrected typo in index
Merge pull request #549 from g-nix/patch-1

Add a section for official standards; add POSIX.
Added Just Enough Ruby to Get By
Merge pull request #552 from serv/master

Added Just Enough Ruby to Get By
add new books
Add Alphabetizing
Update free-programming-books-zh.md

added a few more Chinese resources:
   - The Little MongoDB Book 中文版
   - 文章《Functional Programming For The Rest of Us》的中文翻译
Add Operating Systems book
Add Wizard Code book
Merge pull request #557 from JIghtuse/master

Add two books on OS and low-level programming
Merge pull request #556 from justinyhuang/patch-1

Update free-programming-books-zh.md
Alphabetizing English Index & 1 fix
2 link fixes
Merge pull request #558 from MHM5000/master

Alphabetizing and 3 fixes
fix Java related link in the Javascript section
Add effective django