update cdc example

hardware/digistump/avr/libraries/DigisparkCDC/examples/Echo/Echo.ino

@@ -2,7 +2,6 @@
 void setup() {                
   // initialize the digital pin as an output.
   SerialUSB.begin(); 
-  SerialUSB.println("CDC Test");  
 }
 
 // the loop routine runs over and over again forever:
@@ -12,5 +11,11 @@ void loop() {
     SerialUSB.write(SerialUSB.read());
   }
   
-   SerialUSB.delay(10);               // keep usb alive // can alos use SerialUSB.refresh();
+   //SerialUSB.delay(10);
+   /*
+   if you don't call a SerialUSB function (write, print, read, available, etc) 
+   every 10ms or less then you must throw in some SerialUSB.refresh(); 
+   for the USB to keep alive - also replace your delays - ie. delay(100); 
+   with SerialUSB.delays ie. SerialUSB.delay(100);
+   */
 }