Update README with link to slides

Author: robertsmieja

README.md

@@ -2,4 +2,6 @@ Apache Commons Demo
 ===================
 [![Build Status](https://travis-ci.org/robertsmieja/apache-commons-examples.svg?branch=master)](https://travis-ci.org/robertsmieja/apache-commons-examples)
 
-This is a repository containing various examples of different Apache Commons libraries.
+This is a repository containing various examples of different Apache Commons libraries, used alongside a presentation.
+
+The slides for the presentation can be found [here](https://docs.google.com/presentation/d/1pNIXsJHyWmcfRFaYsAU0g7iX_yKdJeevSI-fgV3d9KE/edit?usp=sharing)