added uml

README.md

 
 ### Building a basic `PhoneBook` class
 
+### Building a basic `PhoneBook` class
+
+![PhoneBookDesign](./PhoneBookUML.png)
 
+In this diagram, C stands for Class, f stands for field, and m stands for method.
+So, it can give you a specification for the class and the things it needs to do.
 
 * Create a `PhoneBook` class that holds names and phone numbers.
 * You can use an [associative data type](https://en.wikipedia.org/wiki/Associative_array) (one which stores items as keys paired with values).