Finish STUN implementation

* Do not increment component id (this is used for marking RTP/RTCP)
* Add STUN to all examples so that they work out of the box
* Cast Addr from STUN client to UdpAddr instead of parsing

examples/save-to-disk/main.go

@@ -27,7 +27,13 @@ func main() {
 	/* Everything below is the pion-WebRTC API, thanks for using it! */
 
 	// Create a new RTCPeerConnection
-	peerConnection, err := webrtc.New(&webrtc.RTCConfiguration{})
+	peerConnection, err := webrtc.New(&webrtc.RTCConfiguration{
+		ICEServers: []webrtc.RTCICEServer{
+			{
+				URLs: []string{"stun:stun.l.google.com:19302"},
+			},
+		},
+	})
 	if err != nil {
 		panic(err)
 	}