Automatically redirect to https on tornadoweb.org

[supakeen]

Hi,

very minor gripe maybe even a nitpick is that tornadoweb.org serves on both http and https. I'd prefer it to redirect to https on any http request.

I've enclosed a pull request to at least point the default README.rst link to https.

[bdarnell]

The docs are hosted by readthedocs.org, so this is up to them. I already have the "always use HTTPS" box checked, but it doesn't seem to be working.