Feature for passing objects in URL::route

Add the possibility to generate the URL for a route like
`['path' => '/users/{user}', 'name' => 'users.index']`
with this call:
`URL::route('users.index', ['user' => User::first()])`
instead of this one:
`URL::route('users.index', ['user' => User::first()->id])`

_It is just a little simplification..._