[1pt] Team member #1: Create book and label classes

[Vana Seraydarian]

• Create a Book class in a separate .rb file.
• Create a Label class with an association to the Item class (in a separate .rb file).
  • All Book class properties visible in the diagram should be defined and set up in the constructor method.
  • All Label class properties visible in the diagram should be defined and set up in the constructor method.