Added a new Scala book (#2565)

* Added a new Scala book

"Functional programming for mortals" is a very good book about Scala and it is free to read on the web.

* Removed the '*' at the end

free-programming-books.md

@@ -2089,6 +2089,7 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [EAI Patterns with Actor Model](https://github.com/alexanderfefelov/eai-patterns-with-actor-model) - Vaughn Vernon
 * [Effective Scala](https://twitter.github.io/effectivescala/)
 * [Essential Scala](http://underscore.io/books/essential-scala/) - Noel Welsh and Dave Gurnell (PDF, HTML, EPUB) *(Just fill the fields with any values)*
+* [Functional Programming for Mortals](https://leanpub.com/fpmortals/read) - Sam Halliday
 * [Learning Scala in small bites](http://matt.might.net/articles/learning-scala-in-small-bites/)
 * [Learning Scalaz](http://eed3si9n.com/learning-scalaz/)
 * [Pro Scala: Monadic Design Patterns for the Web](https://github.com/leithaus/XTrace/tree/monadic/src/main/book/content/)