Two new features - HTTPS support and 'dry run' mode.

Hi Michael,

I've added a couple of small features you might like:

1. Support for HTTPS URIs - checks the scheme, and if https is detected, turn on SSL in the Net::HTTP#start call (commit a1317eeed71c8b901c5e9bc79160778a330a3c97)
2. Support for 'dry run' mode - no bookmarks are deleted when a 404 is returned - just log it like any other non-200 response code (commit 4038306b968c13dd18058182c79e1e5590b95428)

I've also added these features to the master branch - if you would like me to submit a pull request there as well as/instead of here, let me know.

Cheers,
Tony.