Update README.md

README.md

 # Student, Instructor, Classroom
 * **Purpose** - to demonstrate the use of [Java interfaces](http://tutorials.jenkov.com/java/interfaces.html#java-interface-example)
-* **Objective** - to implement a `ZipCodeWilmington` class which _mediates_ a _composite_ `Students` and `Instructors` _singleton_ reference.
+* **Objective** - to implement a `ZipCodeWilmington` class which _[mediates]_(https://en.wikipedia.org/wiki/Mediator_pattern) a _composite_ `Students` and `Instructors` _singleton_ reference.
 
 
 ### Part 1.1 - Create `Person` Class