code: function filter(filename) {
  	if (/^polymer-starter-kit-/.test(filename)) {
  		filename = filename.slice(filename.indexOf('\/') + 1);
  	}
  
  	return /^__MACOSX\//.test(filename) ? null : filename;
  }
docs: filter a filename in PSK zip. skipping leading path or __MACOSX dir