setBaseURL() on Restangular obj

The documentation states that we can set the baseURL of Restangular after configuration.

````javascript
app.run(function(Restangular, BaseUrlCalculator) {
    Restangular.setBaseUrl(BaseUrlCalculator.calculate());
});
````

I added the setBaseUrl fn to the Restangular object to make the documentation correct. Now we can change the baseURL during runtime.