Transfer releases.clojars.org to disk

[tobias]

The repo is currently under @ato's AWS account - we should pull it down to the local disk until we figure out where it will live next. This requires:

• configuring nginx to serve the repo
• pointing the CNAME at the server
• updating the promote task to copy to the on-disk repo instead of pushing to s3

[tobias]

I think the approach here would be:

1. temporarily disable promotion
2. pull existing repo to disk
3. adjust cname + nginx config to serve repo from disk
4. reenable promotion, but with code that now copies to the new on-disk repo instead of pushing to s3

I've written a script for pulling down the repo that is idempotent, and am running it now. We can run it again after disabling promotions to get any artifacts promoted between now and then.

[tobias]

Since the classic repo is a superset of the releases repo, we don't need to copy the releases repo after all - we should be able to just point the releases.clojars.org cname at clojars.org. And if we drop promoting (see #415), we don't need to modify the promotion code at all - we can just delete it.

[tobias]

This is pretty much done, I just need to finish updating DNS (which has been impacted by the linode DDoS).

[tobias]

Done - promotion is now disabled, and releases.clojars.org now resolves to clojars.org.