Fixed the review comments

1) Renaming the cartCollection variable name to cartProductCollection.
2) Changing the find("tbody:last") to find("tbody") in the js file and
adding <thead> in the html file.
3) Removing the cartModel and replacing with "product" from
productModel.
4) Renaming files name (cartCollection.js and productCollection.js ) to
cartProductCollection.js and productCatalog.js.
5) Removing the extra added line for getting the quantity and using the
currentTarget.
6) Removing the line find("tr").gt(0).