core: Remove no longer needed the codes
Remove the codes for compatibility
Fix to work the test that order complete from customer
core: Remove the unnecessary column
core: Add options to quantity column of stocks

- Add null false
- Add default value: 0
rspec: Add test case for the stock subtraction
core: Add null false to product_id column of stocks
Merge pull request #53 from hyoshida/remove-todo-task

Remove todo task