Add support to rename headers

[kaue]

var jsonexport = require('jsonexport');

var contacts = [{
    name: 'Bob',
    lastname: 'Smith',
    address: {
       number: 1 
    }
},{
    name: 'James',
    lastname: 'David'
},{
    name: 'Robert',
    lastname: 'Miller'
},{
    name: 'David',
    lastname: 'Martin'
}];

jsonexport(contacts, {
   headers: ['lastname', 'name', 'address.number'],
   rename: ['Last Name', 'Name', 'Address Number']
},function(err, csv){
    if(err) return console.log(err);
    console.log(csv);
});