Options request method.

[satanio]

We might have to implements options method for every valid endpoint, since front-end is very hungry for this information. Now it is managed in nginx/sites-avalaible general settings of the server and this is very unlucky in a way, since it returns the same thing for every options request.
Options request is usually bodiless, returns 204 on success and response contains headers, which tells the "requester" for example what methods are avalaible for that endpoint.
Slim/Route lib can easily manage this, but it should be done in a more robust way and also in a way that allows customization of the returned response.