Make 'add_ingredient' method within UI so that user can add an ingredient to a specific meal.
update menu within list_meals so that user can be directed to choose add_ingredient or list_ingredients.
make a list_ingredients method within the UI for user to view ingredients for a specific meal.
refactor UI in order to fix bugs that would only add ingredients to the last added meal.  Remove local variables within UI. Add menu within 'add_ingredients' method.