Fix another corner case in promote.accept_promotion.

Campaign that has been charged but won't go live until the future must
be updated. Also added a comment for the other corner case.
Bid: add charge_amount property.
gold.py: lookup transactions by user.
Update Babel to 1.0.
Show how many server seconds the user has paid for.
Higher precision version of format_timedelta.
ServerSecondsBar can be made public.
Show gifts received by the user in ServerSecondsBar.
ServerSecondsBar: filter out postcard gold.