Add toQueryString and toQueryParams methods.

Methods to be able to create a URL query string from a hash. Example:
```javascript
_('order:1&date:today').toQueryParams(); // => {order: '1', date: 'today'}
````
Or create a URL query string from a hash. Example:
```javascript
_({order: '1', date: 'today'}).toQueryString(); // => 'order:1&date:today'
````