Create .dateFormatter()

Create format generator method called .dateFormatter().

```javascript
var formatter = Globalize( "en" ).dateFormatter({ date: "short"});

[ new Date( 2014, 0, 1 ), new Date( 2014, 1, 1 ) ].map(function( x ) {
   return formatter( x );
});

// [ '1/1/14', '2/1/14' ]
```

Ref #294
Fixes #297

- [x] Implement
- [x] Docs
- [x] Tests