Add call to #calculate_reorder_date on start

This commit adds a call to #calculate_reorder_date when transitioning to
start that sets the reorder date for new subscriptions, otherwise new
subscriptions never had a reorder date set.
Merge pull request #3 from MettaAudio/fix/set_reorder_date

Add call to #calculate_reorder_date on start
Trying to get tests passing again.