The bug was: If last-updated was not given in the config, the current
date and time was used, inhibiting posting "old" entries.
Todo: Add an option to ask whether "old" entries shall be posted on
first run.
This allows generator-specific handling of e.g. url.
For example in wordpress `id` is an ugly url, while the
speaking permalink is stored in a alternate link
This saves processing time, esp. since for most installation
there should not be so many changes and most times, there will
be zero entries to be posted, thus there is not need to process them.
In a feed typically the newest entries are on top, while the older
ones should be posted first. Thus reverse the order, based on
publish date.
Closes#4.