Deploy to a new S3 bucket
Deploy to a new S3 bucket

CC https://github.com/servo/project/issues/25

The secure variable is generated with:

```sh
echo -n "SECRET" \
  | openssl rsautl -encrypt -pubin -inkey \
  <(curl https://api.travis-ci.org/repos/servo/download.servo.org/key|jq .key -r) \
  | openssl base64 -A
```

… per https://stackoverflow.com/a/48021246
servo/download.servo.org