remove dead links (#3018)

free-programming-books.md

@@ -301,7 +301,6 @@
 * [Elementary Algorithms](https://github.com/liuxinyu95/AlgoXY) - Larry LIU Xinyu
 * [Foundations of Computer Science](http://infolab.stanford.edu/~ullman/focs.html) - Al Aho and Jeff Ullman
 * [Geometry Algorithms](http://geomalgorithms.com) - Dan Sunday
-* [Handbook of Graph Drawing and Visualization](https://cs.brown.edu/~rt/gdhandbook/)
 * [Lectures Notes on Algorithm Analysis and Computational Complexity (Fourth Edition)](https://larc.unt.edu/ian/books/free/license.html) - Ian Parberry (use form at bottom of license)
 * [LEDA: A Platform for Combinatorial and Geometric Computing](http://people.mpi-inf.mpg.de/~mehlhorn/LEDAbook.html) - K. Mehlhorn et al.
 * [Linked List Basics](http://cslibrary.stanford.edu/103/LinkedListBasics.pdf) (PDF)
@@ -1206,7 +1205,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Pro Git Reedited](https://leanpub.com/progitreedited/read) - Jon Forrest
 * [Ry's Git Tutorial](https://web.archive.org/web/20161121145226/http://rypress.com:80/tutorials/git/index) - Ryan Hodson
 * [Think Like (a) Git: A Guide for the Perplexed](http://think-like-a-git.net)
-* [Version Control by Example (Mercurial, Subversion, Verasity)](http://ericsink.com/vcbe/)
 
 
 ### Go
@@ -1277,7 +1275,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Parallel and Concurrent Programming in Haskell](http://chimera.labs.oreilly.com/books/1230000000929/index.html) -  Simon Marlow
 * [Real World Haskell](http://book.realworldhaskell.org)
 * [Speeding Through Haskell](http://www.sthaskell.com)
-* [The Haskell Road to Logic, Math and Programming](https://fldit-www.cs.uni-dortmund.de/~peter/PS07/HR.pdf) (PDF)
 * [Yet Another Haskell Tutorial](http://hal3.name/docs/daume02yaht.pdf) (PDF)
 
 
@@ -1555,7 +1552,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [AngularJs vs EmberJs](http://angularjs-emberjs-compare.bguiz.com)
 * [DockYard Ember.js Style Guide](https://github.com/DockYard/styleguides/blob/master/engineering/ember.md)
 * [Ember App with RailsApi](https://dockyard.com/blog/ember/2013/01/07/building-an-ember-app-with-rails-api-part-1)
-* [Ember.js - Getting started](http://emberjs.com/guides/getting-started/)
+* [Ember.js - Getting started](https://guides.emberjs.com/release/)
 * [Vic Ramon's Ember Tutorial](http://ember.vicramon.com)
 
 
@@ -2099,7 +2096,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Python 3 Tutorial](https://github.com/Akuli/python-tutorial)
 * [Python Cookbook](http://chimera.labs.oreilly.com/books/1230000000393/index.html) - David Beazley
 * [Python Data Science Handbook](https://github.com/jakevdp/PythonDataScienceHandbook) - Jake VanderPlas (HTML, Jupyter Notebooks)
-* [Python for Econometrics](http://www.kevinsheppard.com/images/0/09/Python_introduction.pdf) - Kevin Sheppard (PDF) (2.7.5)
 * [Python for Everybody Exploring Data Using Python 3](http://py4e.com/book.php) - Charles Severance (PDF, EPUB, HTML)
   * [Python for Informatics: Exploring Information](http://www.pythonlearn.com/book.php) (2.7.5)
 * [Python for you and me](http://pymbook.readthedocs.org/en/latest/) (2.7.3)
@@ -2345,7 +2341,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [How to Design Programs](http://htdp.org)
 * [Scheme Tutorial](http://www.cs.hut.fi/Studies/T-93.210/schemetutorial/)
 * [Simply Scheme: Introducing Computer Science](http://www.cs.berkeley.edu/~bh/ss-toc2.html) - B. Harvey, M. Wright
-* [Sketchy LISP: An Introduction to Functional Programming in Scheme](http://www.bcl.hamilton.ie/~nmh/t3x.org/zzz/sketchy-lisp-3rd-ed-pdf.zip) - Nils Holm (ZIP)
 * [Teach Yourself Scheme in Fixnum Days](https://ds26gte.github.io/tyscheme/index-Z-H-1.html)
 * [The Scheme Programming Language: Edition 3](http://www.scheme.com/tspl3/) - [The Scheme Programming Language: Edition 4](http://www.scheme.com/tspl4/)
 * [Write Yourself a Scheme in 48 Hours](https://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours) - Wikibooks