Add some ruby books and courses

* Code Academy Ruby
* How to think like a computer scientist: Learning with ruby
* Ruby in twenty minutes
* Ruby Essentials
* Ruby Learning
Update free-programming-books.md
Merge pull request #167 from thiagoskapata/patch-1

Update free-programming-books.md
Added Andrew Ng's course notes; updated broken link

Ng's materials include problem sets, solutions, handouts/notes, and video lectures.
Fixed broken link for PL/SQL Obsession.
Merge pull request #168 from corragon/patch-1

Added Andrew Ng's course notes; updated broken link
adding some free programming books for brazilians
adding some free programming books for brazilians
Merge pull request #169 from mosampaio/master

creating a pt_BR version (portuguese from brazil)
Added Tango With Django.
Added "Making Games with Python & Pygame" to "free-programming-books.md"
Merge pull request #170 from canibanoglu/add-tango-with-django

Added Tango With Django.
Add portuguese list of books to README
Merge pull request #172 from gabraganca/pt-Br

Add portuguese list of books to README
Merge pull request #171 from adesor/master

Added "Making Games with Python & Pygame" to "free-programming-books.md"
Fix typo
Merge pull request #173 from Miik4chu/patch-1

Fix typo
Update free-programming-books.md

added javascript's http://devdocs.io/
Add german book list (more will follow soon)
Merge pull request #175 from tk120404/patch-1

Update free-programming-books.md
Add german book list to the README