Remove hardrockcoffeescript.org (#2480)

It looks like this domain has been registered to a different owner.

free-programming-books.md

@@ -963,7 +963,6 @@
 
 * [CoffeeScript Cookbook](https://coffeescript-cookbook.github.io)
 * [CoffeeScript Ristretto](https://leanpub.com/coffeescript-ristretto/read) - Reginald Braithwaite
-* [Hard Rock CoffeeScript](http://hardrockcoffeescript.org)
 * [Smooth CoffeeScript](http://autotelicum.github.io/Smooth-CoffeeScript/SmoothCoffeeScript.html)
 * [The Little Book on CoffeeScript](http://arcturo.github.io/library/coffeescript/)