Use ReconciliationSendPayload with maximum peer size

[xash]

Implements this TODO: "We should check if the entry's payload length is less than our partner's maximum_payload_size and send the payload, but at the time of writing time is short and that requires something of a refactor to the announcer."

Announcer passes Payload iff it wants it to be send immediately.

[sgwilym]

Wonderful, this feature saves a lot of roundtrips! Would it be possible to add a test for this, so that we can catch regressions in future?

[xash]

There wasn't a way to test for specific packets except awkwardly capturing console.log's output – so I replaced the log with a onMessage callback that can be used for testing/debugging. Alternative to the callback would be wiretaping the transports between Alfie/Betty and decoding the packets, but that seems to troublesome with the very stateful protocol. Anyway, now there is a proper test for the maximum peer size limit. (-:

[sgwilym]

Wow, thank you. That onMessage callback you added will come in handy.