t/samples.t: add test about handling created_at field.
now "id" field includes the timestamp of the status.
This is because in some feeds, the same item can be updated over and over, and these updates should be treated as different statuses in BusyBird.
Feed: ensure the number of arguments to XML::FeedPP->new() is odd.
$self->{user_agent}->agent method may return an empty list in list context.
What's worse, XML::FeedPP->new behaves very oddly when given even numbered arguments, leading to hard-to-understand bug.
Add Run.pm and busybird_input_feed command-line tool. Pass the test xt/run.t