updated readme

README.MD

@@ -30,3 +30,4 @@ Make all the tests in the `StringUtilitiesTest` class pass. All the methods have
   - `String getLastWord(String value)`
 
 ## Section 3 - Bonus
+This section is optional, but highly encourage you to complete. Make all the tests in the `BonusTest` class pass. All the methods have been stubbed out for you in the `Bonus` class. Each of the method has a comment above it to describe the expected behavior. Look at the test case to see example of input and expected output.