Add pubnub-watching zulip bot

[ekimekim]

Which also records all pubnub messages for archival to a file SEGMENTS/pubnub-log.json. We ran this for most of last year, but not as part of wubloader.

In that file, we wrap raw pubnub messages in a metadata object containing:

• time
• our hostname
• our pid
• any inferred information

Plus make a message-less log write on startup so we know where there might be gaps.

Fixes #394 Fixes #395

[ekimekim]

Unfortunately not possible to fully test until this year's site is active and people are donating.