Add Contact info section

README.md

@@ -1739,3 +1739,9 @@ Special thanks to:
 * [System design cheat sheet](https://gist.github.com/vasanthk/485d1c25737e8e72759f)
 * [A distributed systems reading list](http://dancres.github.io/Pages/)
 * [Cracking the system design interview](http://www.puncsky.com/blog/2016/02/14/crack-the-system-design-interview/)
+
+## Contact info
+
+Feel free to contact me to discuss any issues, questions, or comments.
+
+My contact info can be found on my [GitHub page](https://github.com/donnemartin).