Using itertools.takewhile() on a NodeIterator returns a plain Iterator,
and so it's not resumable.
The strategy has been altered to pass an extra argument to
posts_download_loop, a lambda that is evaluated for each post, and
causes the loop to stop when it returns false.
While this isn't really an error, it requires user action, so the message
is printed to stderr even with --quiet, and repeated at the end when that
option is not enabled.
Resolves#1159.
Adds the --latest-stamps command line option, pointing to a file where
the latest time each profile was scraped. On the next run, only posts
newer than that time are downloaded.
Fixes#1122.
Eduardo Kalinowski