Add 'Ruby on Rails' section and 'El maldito libro de los Descarrilados' book
merge assembly with "ensamblador"

both catergories are the same. I also put the title of Lisa Watts's book in spanish (as the translations version has)
Merge pull request #462 from mgaitan/patch-1

merge assembly with "ensamblador" (spanish list)
Add index for 'Ruby on Rails' section.
Merge pull request #461 from Chakaitos/master

Update free-programming-books-es.md - new resource