New Handler: WhatFailureGroupHandler

I believe this handler provides a workaround for https://github.com/Seldaek/monolog/issues/368 this is a concern for us as well and rather than have our service fail completely because a connection to a remote TCP endpoint (logstash) and rather than sacrifice speed by closing/reopening connections regularly, this seemed like a reasonable compromise to me.
I don't think this handler should be in ``src`` given that it is not usable in a real use case