Fails to handle broker outage (or wrong url)

If the configured MQTT broker cannot be reached (either it has been incorrectly specified host/port in the code, or it is down), then the web page returned by Ruby will print an inelegant error page.

Errno::ECONNREFUSED at /
Connection refused - connect(2)
file: client.rb location: initialize line: 127

This could be handled more gracefully.
