Implemented a new tick function
Added PM LED on pin 13. Switch to time set
Fixed button press issue with new function
Implemented alarm, flashes for now. Button off

For now the alarm flashes each half second. Eventually this should be
joined by a buzzer. Made it so pushing button goes to time disp mode.
Next features should be buzzing alarm, snooze/disable, and double click
to turn on alarm.
Added alarm tone and changed time set transitions

Now when in either time set mode, hold down button for 3 seconds to
switch between time set and alarm set.
Implemented alarm status LED