Add Learn Markdown

I added "Learn Markdown" and created the Markdown section.
Add "Compiling Techniques" by F.R.A. Hopgood
Adds Building REST APIs with Rails book
Merge pull request #1037 from diegowifi/master

Add Learn Markdown
Adding Markdown to Index #1037
Merge pull request #1041 from chastai/add-book

Add "Compiling Techniques" by F.R.A. Hopgood
Merge pull request #1043 from kurenn/master

Building REST APIs with Rails
Merge pull request #1044 from maieul/master

Apprendre l'informatique sans ordinateur
Added NKS to Cellular Automata Book list
Merge pull request #1045 from estrabd/master

Added NKS to Cellular Automata Book list
I added a few new books here and there. Notably, I created entries
for these new languages: Alef, Chapel, Cilk, Limbo, and OpenMP.
Merge pull request #1046 from estrabd/master

I added a few new books here and there. Notably, I created entries
Added backbone.js book
Add Apprenticeship Patterns
Merge pull request #1049 from suzannehamilton/apprenticeship-patterns

Add Apprenticeship Patterns
Update free-programming-books-tr.md
Merge pull request #1050 from leylaKapi/master

Update free-programming-books-tr.md
Update free-programming-books-tr.md with iOS source
Merge pull request #1048 from arthurvr/master

Added backbone.js book
Merge pull request #1051 from ArslanBilal/patch-1

[tr] - iOS