The change to use UTC broke the test

The order deadline is stored in UTC but we were comparing it to the
local timezone to decide if we need to close it.

* Closes: #27

Cents should be negative as well.

* Closes: #17

* Closes: #22

* Closes: #19

* Closes: #23

* Closes: #20

As we are changing the list of products

So we can modify expired orders

* Closes: #16