_.pluck extended to support fetching multiple properties

This seems like an intuitive functionality. Example:

var people = [{first : 'moe', last: 'doe', age : 30}, {first : 'curly', last: 'brackets', age : 50}];
_.pluck(people, 'first'); // returns ['moe', 'curly']
_.pluck(people, ['first', 'last']); // returns [ ['moe', 'doe'], ['curly', 'brackets'] ]

Performance impact: 20% slower