fix https://rust-lang.org redirect

[edunham]

We manage our own DNS. This issue is a note to myself that it would be aesthetically nice to cause https://rust-lang.org to point at https://www.rust-lang.org . It's low-priority, since https://rust-lang.org should not be linked from anywhere.

• www.r-l.o points at cloudfront, where the front page and docs are served from.
• rust-lang.org points at the nginx proxy server, which munges URLs and redirects users to the appropriate sites
• all links meant to point at the front page should already be of the form www.r-l.o, which is a CNAME directly to cloudfront. This means most users will still be able to access the site even if the proxy is unavailable
• Correctly fixing this will require updating nginx configs and changing the @ redirect to a CNAME in DNS (I think, though troubleshooting could potentially interrupt access to all r-l.o sites)

[tbu-]

https://rust-lang.org/ doesn't work for me at all. "Unable to connect." Probably no one is listening on the HTTPS port on rust-lang.org.

[hsivonen]

I filed a bug in Bugzilla in the hope that it works better as the avenue for server config (as opposed to content) changes.