This handles incoming events (for now only ProposalCreated, but easy to
extend), and moves the channel message for new proposals to the event
handler, so that they're being announced for all proposals, including
those created manually from kredits-web for example.
No idea why, but on the server, all data is contained within a single
'payload' property, while I've never seen any such property on my
machine. Could be different node or express versions, but in any case,
this should fix it so that it just works no matter what.
