Updating readme index.

Author: cpowell

README.md

@@ -16,6 +16,7 @@ The RECF has been documented in a series of blog posts by the author:
 * [Part 5 - libGDX concepts](http://cbpowell.wordpress.com/2012/12/11/entity-component-game-programming-using-jruby-and-libgdx-part-5/)
 * [Part 6 - the Lunar Lander game](http://cbpowell.wordpress.com/2012/12/13/entity-component-game-programming-using-jruby-and-libgdx-part-6/)
 * [Part 7 - serialization](http://cbpowell.wordpress.com/2012/12/16/entity-component-game-programming-using-jruby-and-libgdx-part-7/)
+* [Part 8 - collision detection and more](http://cbpowell.wordpress.com/2012/12/17/entity-component-game-programming-using-jruby-and-libgdx-part-8/)
 
 # Are you using this in a game?
 Won't you consider emailing the author at <[email protected]> ? I'd love to