Slight cleanup in mailer function
Fixed a major bug related to last_date popping.

Was sorting the manytomany next_date query set the wrong way, causing
the date_update task to pop dates off the *farthest* date (for foods
with more than one known date). Thus, the only foods showing up in the
recent tab were ones with only one known date when date_update was run
on them. Will read my queryset docs more closely next time.