Project 04: Generated Cart scaffold and products

Project 04:
Iteration D1:
  Generated Cart scaffold, made it so that the current cart is stored in
  the session with a cart_id index and that new carts are created and
  destroyed when needed
Iteration D2:
  Generated Line Items to create a relationship between carts and
  products. Created the relationship between the three.

Looks like this never got committed. :\