finished get product detail, create product, but cannot test product comment (too much recusion levels)
open a new branch to store the db connection on "g"
Switch by using db_session and use it from "from database import db_session" to g.db
and fixed all of the 9 test cases (create_product_comment)
Finished the investment of users on products
1. Use Association instead of using many-many relationship on investment
Little refactor - remove the dependencies on object "Investment"
Finishd like function
Remove redundant dependencies on like.py
Finished Tag Model. Ready to go for tag view