fix to allow more than one list's tasks to be written to new class

The re-use of "tasks" variable name was causing the "tasks" inside the for-loop to overwrite the main tasks variable (from the response of send_requests) to be overwritten. 

This caused only one non-inbox list to be populated after a successful Wunderlist query. (The inbox list is populated before the for-loop is entered, so you get the inbox + the first iteration of the for loop.)