No more bare except blocks.
More graceful handling of missing datetime.

So I remembered why boottime originally returned a time.struct_time
object instead of a datetime.datetime one (issue #1): Plan 9's most
readily available Python is so old it doesn't yet have the datetime
module.

We officially definitely don't support Python 2.2, but I'd really like
to keep Plan 9 support. There's talk of a 2.7 port, but I'm not sure
that's ready yet. So.
Version bump for boottime's new return type.