Bug with backscroll on first join

[Alexander Cobleigh]

it looks like people are having an issue with not seeing any backscroll when they first start cabal up and enter a populated channel

rejoining the channel using /change <channel> fixes it

there's probably some little tweak needed in neat-screen

(maybe we need to attach a listener to self.cabal.db.on('append', cb) & self.cabal.db.on('remote-update', cb) ?)

[hunor karamán]

little note, but not just on first join, but on every join if there are more than 1 new messages.