Allow broadcasting to different destinations

[DonDebonair]

It would be great if Athena could broadcast to different destinations, such as Slack, Email, HipChat etc. This should be possible from the CLI, but additionally could also be hooked into the scheduling system (send small reports to Slack periodically!) athena mail should probably be renamed to athena broadcast.

[DonDebonair]

athena mail has for now been renamed to athena report. We should think about a generic way to handle reports & broadcasts to multiple possible destinations