Wait for sends to complete in ConnectionListener

[randomPoison]

Right now, connection listener tries to send messages without waiting for the send to complete. This results in messages not being sent when they should be. This is especially dangerous now that ConnectionListener acts as a broker between the server socket and the client socket, so dropping a packet means the communication between the two is delayed or lost.

We should do something to ensure that sends complete properly (though I'm not entirely sure what). We should reference UdpFramed to see how a type that is both Send and Sink should operate.