Date format in grade setting example

[drlippman]

In the example of how to use the grade service, the readme has

->set_timestamp(date(DateTime::ISO8601))

But the AGS specs say "Timestamp values MUST be formatted using ISO 8601 with a sub-second precision." and the DateTime::ISO8601 format does not include sub-second precision. Also (at least according to php manual) DateTime::ISO8601 isn't actually iso8601 compatible.

I'm guessing most platforms can handle the dates as this example sets them so it's probably OK, but I think a more accurate timestamp setting would be:

->set_timestamp(date('Y-m-d\TH:i:s.uP'))

which is the DateTime::ATOM format with the addition of sub-seconds.