create a page that shows dial frequency for active payloads

[danielrichman]

With the latest dl-fldigi update, people will be uploading dial frequency, audio frequency, etc.

A quick blob of coffeescript, maybe a map or reduce or something if necessary, and we could have a live updating page showing dial frequency. This is often requested and I think people would find it useful.

Then (joke warning), at the request of @eroomde, we could have griffonbot report live frequencies to IRC :-P.