Fixed reset issue when opening serial connection

Added while(!Serial) to setup() to prevent board from resetting when connecting to its USB-serial interface

traffic-light-arduino.ino

@@ -45,6 +45,8 @@ void setup() {
   // initialize the serial connection
   Serial.begin(115200);
 
+  while(!Serial);
+
   Serial.println(F("\n# Serial started"));
 
   Serial.print(F("# Build Date: "));