Get Box object, representing list of objects in a folder.

def listdir(self, folder_id='0', offset=None, limit=None, fields=None):
		'Get Box object, representing list of objects in a folder.'
		if fields is not None\
			and not isinstance(fields, types.StringTypes): fields = ','.join(fields)
		return self(
			join('folders', folder_id, 'items'),
			dict(offset=offset, limit=limit, fields=fields) )