Adds GA Dash

Dash is a new site that I'm working on to teach HTML and CSS. Try it out and merge if you like it!

free-programming-books.md

@@ -316,6 +316,7 @@
 
 * [Dive Into HTML5](http://fortuito.us/diveintohtml5/)
 * [HTML Dog Tutorials](http://www.htmldog.com/)
+* [GA Dash](http://dash.generalassemb.ly)
 
 
 ###Java