Generated & migrated Invoice model/table
Added implementation to do list in README
small change to product_id migration, added to README
Generated & migrated Employee model/table
Added employee_id to Sales, updated README to do list
Added account_no and name to Customers
Dropped customer_and_account_no from Customers
merged in Employees branch & fixed conflicts in schema.db
marked some tasks done
removed drop customer info from Customers table, rolled back to first migration
Deleted null constraints on Customers migration; updated migrations to include reset_column_information line where migrations were previously not working when I ran them all at once