Support datadog event format

[Xosmond]

It would be nice we could format messages for events on datadog.

Documentation: https://docs.datadoghq.com/developers/dogstatsd/datagram_shell?tab=events

If no-one took this before, I'm happy to add it :)

[miketheman]

Sounds interesting! Feel free to take a stab at it. Not that you should add the applicable spec tests as well, preferably before adding the code.