Add support for `formatOptions` as a second arg to intlNumber/Date

This allows for the following:

**server.js:**

```js
var locales = ['en-US'], 
    formats = {
        number: {
            usd: {
                style   : 'currency',
                currency: 'USD'
            }
        }
    };

res.render({
    i18n: {
        locales: locales,
        formats: formats
    }
});
```

**template.hbs:**

```
{{#intl locales=i18n.locales formats=i18n.formats}}
    {{intlNumber 1000 'usd'}}

    or

    {{intlNumber 1000 @intl.formats.number.usd}}
{{/intl}}
```