Adding buzzer support

I thought that since Sous Vide takes a long time, a buzzer would be a good method of notifying the user of temperature fluctuations even if you are not in the room.
This provides the functions `setBuzzer()` and `buzzer(int state)`, and a state variable `buzzerState` as a handle for other functions.
By default, the high alarm is 1 degree, and the low alarm is 0.2 degrees. The buzzer pin is `D7`.