Add mqtt over TLS support

[peyoot]

add additonal MQTT_TLS flag and CA, cert, key file in settings.py
tested mqtts support and it works fine!

[lbt]

In principle these changes are acceptable. However they cannot be merged in this PR.

Please update the README to add information to this upstream rather that as if you were forking it.

The settings for MQTT_TLS should handle the setting being undefined.
The mqtt.connect() should handle SSL and non-SSL
Don't change the author/email/packages in setup.cfg

Thanks

(Also apologies for the slow response - this project's emails were going into my low-priority folder)