Update README.md

Author: mpmenne

pset2/README.md

@@ -10,6 +10,7 @@ What to do:
 
 * Refactor your existing Mario to use proper Java packages.  Open your project in an IDE (preferably Intellij IDEA)
 * Check out the following video on how to create a [Java project in under 4 minutes](http://tv.launchcode.us/#/videos/java_game_10min?lesson=Java) 
+* Also watch the following videos on Strings [Strings](http://tv.launchcode.us/#/videos/java_strings?lesson=Java) and [String Performance](http://tv.launchcode.us/#/videos/java_strings_performance?lesson=Java).  Feel free to refactor your code accordingly.
 * Implement the functionality mentioned in the summary.  When complete, commit and push to your repository.
 * You should notice that your code has lots of if statements... we're going to get rid of those by using the Strategy Design Pattern
 * Watch the video [Strategy Design Pattern in Java](http://tv.launchcode.us/#/videos/java_strategy?lesson=Java)