Applied OOP to create Person, Author, and Grocery classes

This is a bit redundant. When using a getter method, you'd run it like: `@user.name` which in your case would return Liz.

With this code, we would have to run `my_groceries.grocery_list` which would then return the list. It may be easier to understand this if we change `@grocery_list` in `initialize` to `@items`. Then this would make more sense: `my_groceries.items`