Update comments in examples (#457)

It's seems not that important, but this helps the new user understand the code.

examples/DumpInfo/DumpInfo.ino

@@ -51,7 +51,7 @@ void setup() {
 }
 
 void loop() {
-	// Look for new cards
+	// Reset the loop if no new card present on the sensor/reader. This saves the entire process when idle.
 	if ( ! mfrc522.PICC_IsNewCardPresent()) {
 		return;
 	}