Reuse last resource from url dispatch table

If name and path is the same -- add a route to existing resource instead of creating a new one.

E.g.
```
router.add_get('/', ...)
router.add_post('/', ...)
```
should create the single resource if path and name are the same.

It reduces resources table size and boosts url lookup if handlers for the same url is grouped together.

The change is easy, Pull Request is welcome.