Underscore: Add function to rename keys in objects

Add function to rename keys in an object

> var _ = require('underscore');
> var note = {
... '_id': 1,
... 'title': 'Ruby is awesome..',
... 'text': '..and so is CoffeeScript'
... }
> console.log(_.rename(note, [['_id', 'id']]));
{ id: 1,
  title: 'Ruby is awesome..',
  text: '..and so is CoffeeScript' }

or an array of objects

> var notes = [note, note];
> console.log(_.rename(notes, [['_id', 'id']]));
[ { id: 1,
    title: 'Ruby is awesome..',
    text: '..and so is CoffeeScript' },
  { id: 1,
    title: 'Ruby is awesome..',
    text: '..and so is CoffeeScript' } ]

Thanks,
Nisanth