getHistory() {
		return this.call('get_clean_summary')
			.then(result => {
				return {
					count: result[2],
					days: result[3].map(ts => new Date(ts * 1000))
				};
			});
	}
Get information about the cleaning history of the device. Contains
information about the number of times it has been started and
the days it has been run.