build/lib/stats.ts/createStatsStream
export function createStatsStream(group: string, log?: boolean): es.ThroughStream {

	const entry = new Entry(group, 0, 0);
	_entries.set(entry.name, entry);

	return es.through(function (data) {
		const file = data as File;
		if (typeof file.path === 'string') {
			entry.totalCount += 1;
			if (Buffer.isBuffer(file.contents)) {
				entry.totalSize += file.contents.length;
			} else if (file.stat && typeof file.stat.size === 'number') {
				entry.totalSize += file.stat.size;
			} else {
				// funky file...
			}
		}
		this.emit('data', data);
	}, function () {
		if (log) {
			if (entry.totalCount === 1) {
				fancyLog(`Stats for '${ansiColors.grey(entry.name)}': ${Math.round(entry.totalSize / 1204)}KB`);

			} else {
				const count = entry.totalCount < 100
					? ansiColors.green(entry.totalCount.toString())
					: ansiColors.red(entry.totalCount.toString());

				fancyLog(`Stats for '${ansiColors.grey(entry.name)}': ${count} files, ${Math.round(entry.totalSize / 1204)}KB`);
			}
		}

		this.emit('end');
	});
}