added model, migration, and test for orders
added model, migration, and test for cart
added migration, model, and test for menu items
fixed association between cart and order
changed uniqueness validation on menu item name
fixed user naming conflicts
Merge pull request #2 from markmccanna1/shopping_cart

Added Menu Item, Order, and Cart for Shopping Cart Functionality
merged files from master after cart and items added
fixed database create table in categories