Argument processing

Set up the command line arguments, logging,
and the pinboard client.

Signed-off-by: Doug Hellmann <doug.hellmann@gmail.com>
Set up processing threads

Start setting up the processing threads, including
a worker to retrieve the bookmarks from pinboard.in
and filter them to see which the user wants updated.

Signed-off-by: Doug Hellmann <doug.hellmann@gmail.com>
change dry-run message

Signed-off-by: Doug Hellmann <doug.hellmann@gmail.com>
change wait to join for threads

Signed-off-by: Doug Hellmann <doug.hellmann@gmail.com>
Check and rewrite links

Use the requests library to look for redirects for
links and replace them as appropriate.

Signed-off-by: Doug Hellmann <doug.hellmann@gmail.com>
improve logging and error handling

Signed-off-by: Doug Hellmann <doug.hellmann@gmail.com>
Add --add-only option

Add a new option to only add new links, without removing the old
ones that redirect.

Signed-off-by: Doug Hellmann <doug.hellmann@gmail.com>