Add Intro to Programming with Ruby book

free-programming-books.md

@@ -1865,6 +1865,7 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [CodeCademy Ruby](https://www.codecademy.com/learn/ruby)
 * [Developing Games With Ruby](https://leanpub.com/developing-games-with-ruby/read)
 * [I Love Ruby](http://goo.gl/1qrMUN)
+* [Introduction to Programming with Ruby](https://launchschool.com/books/ruby) - Launch School
 * [Just Enough Ruby to Get By](http://jasonkim.ca/projects/just_enough_ruby_to_get_by/)
 * [Learn Ruby the hard way](http://learnrubythehardway.org/book/)
 * [Learn to Program, by Chris Pine](http://pine.fm/LearnToProgram/)