[HTTPS-Everywhere] Adding HTTPS to the ShareThis service

[mezzanine at Safe-mail.net]

With the ShareThis service, it has been said that HTTPS can be supported by substituting
the ws.sharethis.com domain in place of the w.sharethis.com domain. For more details,
please see http://forums.sharethis.com/topic.php?id=3033&replies=7#post-5976 on the Web. Assuming that to do so would be compatible with the ShareThis terms of service,
implementing the previously-mentioned domain remapping should be possible via a
simple ruleset.

--Richard