Add _uri and _method in variables

* `_uri` is the routed URI, very useful to get it because it can be different of `getURI()`,
* `_method` is the current method, can be different of `getMethod()` in case of a HVMC, and also allows to use `Hoa\Router` and `Hoa\Dispatcher` to make [RMR](http://www.peej.co.uk/articles/rmr-architecture.html).

Asking @camael24 for a review :-).