Initial commit: minimal relay server and CLI structure

Relay pairs connections by room name and pipes bytes between them,
with no password/PAKE handshake at the relay layer — codephrase-based
encryption is left to the client side of the transfer.

src/tcp/defaults.go

@@ -0,0 +1,9 @@
+package tcp
+
+import "time"
+
+const (
+	DEFAULT_LOG_LEVEL             = "debug"
+	DEFAULT_ROOM_CLEANUP_INTERVAL = 10 * time.Minute
+	DEFAULT_ROOM_TTL              = 3 * time.Hour
+)