Added another todo

Author: Mitch1404

todo.txt

@@ -5,9 +5,4 @@
  - Might be a good idea to ensure the course cost in the database, matches with the amount paypal says is being paid. (Currency type makes this possibly quite annoying).
  - When paypal duplicate txn id is detected, report error. There might be something amiss other than paypal double sendign the reply.
  - Translate PayPal payment_date into unix timestamp, instead of current implementation of getting time() once IPN is received.
-
-// Known / Predicted Issues
- - 
-
-// Known Bugs
- - 
+ - Add checks for when the Paypal subplugin is in sandbox mode. So students dont by courses when the subplugin is in sandbox mode and such.