* Replace supervisord xmlrpc library
* Use `github.com/mattn/go-xmlrpc` that doesn't leak goroutines.
* Fix uptime metric
* Use Prometheus best practices for uptime metric.
* Use "start time" rather than "uptime".
* Don't emit a start time if the process is down.
* Add changelog entry.
* Add example compatibility rules.
Signed-off-by: Ben Kochie <superq@gmail.com>
