Pauses the clock to continue running later.
		Saves the duration of the current interval in the previous_intervals 
		list.

def pause(self):
		""" Pauses the clock to continue running later.
		Saves the duration of the current interval in the previous_intervals 
		list."""
		if self.status == RUNNING:
			self.status = PAUSED
			self.previous_intervals.append(time.time() - self.interval_start)
			self.current_interval_duration = 0.0
		elif self.status == PAUSED:
			self.interval_start = time.time()
			self.status = RUNNING