KeepAlive enhancement.

If the server doesn't send keepalive for 20 seconds, generate an error.
fix #251, close #255

bot/basic/info.go

@@ -76,6 +76,8 @@ func (p *Player) handleLoginPacket(packet pk.Packet) error {
 	if err != nil {
 		return Error{err}
 	}
+	
+	p.resetKeepAliveDeadline()
 	return nil
 }