add "The Python GTK+ 3 Tutorial"
Merge pull request #1064 from taurenchieftain/master

add "The Python GTK+ 3 Tutorial"
Fix formatting
Merge pull request #1066 from uschek/master

Fix formatting
Update CONTRIBUTING.md
Isabelle/HOL - fix anchor link

Anchor link for Isabelle/HOL was not working when viewing the Github parsed file.
Update free-programming-books.md

No longer published
Merge pull request #1070 from olso/patch-1

Update free-programming-books.md
Merge pull request #1067 from codrineugeniu/master

Isabelle/HOL - fix anchor link
Removed duplicate link to Dashing d3.js.
Added a new book on Titan Graph Database

Added a new book on Titan Graph Database
Merge pull request #1072 from ridrees/patch-1

Added a new book on Titan Graph Database
Merge pull request #1071 from chrisspruck/quickedits

Removed duplicate link to Dashing d3.js.
Add section for Meteor with a link to new free book
Merge pull request #1074 from thisisbrianhan/master

Add section for Meteor with a link to new free book
Include PureScript Book
Update free-programming-books.md
Add 2 python books

Learn Python in Y minutes
The Python Ecosystem: An Introduction
Added the famous Gerald's book

プログラミングの理論の項があるべきだと思いこの本を追加させていただきます。

「計算機プログラムの構造と解釈」
プログラミングの根幹をなす様々な理論を学び、実践する力も得られる教科書です。
楽しく、明快に、かつ実践を通して学ぶというMITの信念を体現したような本です。
MITや多くの最高レベルのCS Departmentで教科書として読まれています。
Merge pull request #1076 from paf31/patch-1

Add "PureScript By Example"