Update free-programming-books.md

corrected HTML / CSS link
Learn Vimscript the Hard Way
Merge pull request #17 from MiroslavPetrik/master

Learn Vimscript the Hard Way
Merge pull request #16 from sillero/patch-1

Update free-programming-books.md
Added Category Theory for Computing Science.
Add DTrace book from illumos
Fix embedded Delphi / Pascal link
update dead link to Emacs manual with new link
Merge pull request #18 from jeffdc/master

Added Category Theory for Computing Science.
Merge pull request #19 from demands/patch-1

Add DTrace book from illumos
Merge pull request #20 from demands/patch-2

Fix embedded Delphi / Pascal link
Merge pull request #21 from petrushev/master

Added three books
Merge pull request #22 from farindk/master

update dead link to Emacs manual with new link
Adding in a section for D3.js with a link to "Interactive Data Visualizations for the Web" by Scott Murray
adding graph databases free ebook
adding the little riak book
adding another tour of scala
adding data sorcery with clojure
Merge pull request #24 from ktkaushik/master

adding graph databases, the little riak book and Another tour of Scala
Updating d3.js title to not say node.js