Added books. (#4223)

* Added books.

* Added a PDF annotation.

* Removed trailing slash.

* Removed some things because of Travis CI warnings.

* Update free-programming-books-ta.md

* Added construction in process.

free-programming-books-ta.md

@@ -16,7 +16,7 @@
 
 ### CSS
 
-* [எளிய தமிழில் CSS](http://www.kaniyam.com/download/learn-css-in-tamil.pdf) (PDF)
+* [எளிய தமிழில் CSS](http://www.kaniyam.com/download/learn-css-in-tamil.pdf) - Kaniyam Foundation (PDF)
 
 
 ### Database

free-programming-books.md

@@ -284,8 +284,10 @@
 * [Graphics Programming Black Book](http://www.gamedev.net/page/resources/_/technical/graphics-programming-and-theory/graphics-programming-black-book-r1698) - Michael Abrash
 * [Introduction to Modern OpenGL](https://open.gl)
 * [Introduction to TouchDesigner 099](https://leanpub.com/introductiontotouchdesigner/) *(Leanpub account or valid email requested)*
+* [Learn Computer Graphics From Scratch!](https://www.scratchapixel.com) - Scratchapixel (:construction: *in process*)
 * [Learn OpenGL](http://learnopengl.com) - Joey de Vries
 * [Learning Modern 3D Graphics Programming](https://web.archive.org/web/20150225192611/http://www.arcsynthesis.org/gltut/index.html) - Jason L. McKesson (draft)
+* [Notes for a Computer Graphics Programming Course](https://www.cs.csustan.edu/~rsc/CS3600F00/Notes.pdf) - Dr. Steve Cunningham (PDF)
 * [OpenGL](http://www.songho.ca/opengl/index.html) - Concepts and illustrations.
 * [ShaderX series](http://www.realtimerendering.com/resources/shaderx/) - Wolfgang Engel
 * [Tutorials for modern OpenGL](http://www.opengl-tutorial.org)
@@ -2756,6 +2758,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 * [An Introduction to Unix](http://www.oliverelliott.org/article/computing/tut_unix/)
 * [Commentary on the Sixth Edition UNIX Operating System](http://www.lemis.com/grog/Documentation/Lions/) - J. Lions
+* [INTRODUCTION TO UNIX](https://homepages.uc.edu/~thomam/Intro_Unix_Text/TOC.html) - Mark A. Thomas
 * [Unix as IDE](https://github.com/mrzool/unix-as-ide) - Tom Ryder (epub, mobi)
 * [UNIX Commands and Concepts](http://www.cs.bu.edu/teaching/unix/reference/) - Robert I. Pitts
 * [Unix for Poets](http://web.stanford.edu/class/cs124/kwc-unix-for-poets.pdf) - Kenneth Ward Church (PDF)