Wait for serial port to be ready

From issue #153 (closed):

BTW - you say that this library works on "every arduino board" and so I would add this in your examples:

void setup() {
 Serial.begin(9600);
//  while (!Serial); // this line needs to be in setup for leonardo and Yun to work
// here goes the rest of your example

Without this while loop your example sketch works, but nobody can see it, since Yun doesn't restart/wait for the serial to open connection, and executes setup function right after the sketch is being uploaded to the board.