This is necessary for using Keter as a front-end to other web
services that may require hacks like Jenkins does, where the
"Location" header needs to be rewritten to use https on every
response.
Example:
```
root: ..
port: 80
ssl:
# host:
port:
key:
certificate:
reverse-proxy:
- reversed-host: jenkins-internal.corp.example.com
reversed-port: 8080
reversing-host: jenkins.example.com
ssl: False
rewrite-response:
- header: Location
from: ^http://jenkins.example.com
to: https://jenkins.example.com
```