Github commit status: use the last one for reals

Github keeps changing the order of commit statuses it returns. This
change sorts them so we don't care about the returned order.

'id' is a monotonically increasing int, so it's easy.
Merge commit-status-choose-last-for-real (#110) into master

Github commit status: use the last one for reals

Github keeps changing the order of commit statuses it returns. This
change sorts them so we don't care about the returned order.

'id' is a monotonically increasing int, so it's easy.