Add Mutant deep dive blog post to README.

README.md

@@ -340,13 +340,15 @@ Blog posts
 
 Sorted by recency:
 
+* [A deep dive into mutation testing and how the Mutant gem works][troessner]
 * [How to write better code using mutation testing (November 2015)][blockscore]
 * [How good are your Ruby tests? Testing your tests with mutant (June 2015)][arkency1]
 * [Mutation testing and continuous integration (May 2015)][arkency2]
 * [Why I want to introduce mutation testing to the `rails_event_store` gem (April 2015)][arkency3]
 * [Mutation testing with mutant (April 2014)][sitepoint]
 * [Mutation testing with mutant (January 2013)][solnic]
 
+[troessner]: https://troessner.svbtle.com/kill-all-the-mutants-a-deep-dive-into-mutation-testing-and-how-the-mutant-gem-works
 [blockscore]: https://blog.blockscore.com/how-to-write-better-code-using-mutation-testing/
 [sitepoint]: http://www.sitepoint.com/mutation-testing-mutant/
 [arkency1]: http://blog.arkency.com/2015/06/how-good-are-your-ruby-tests-testing-your-tests-with-mutant/