index.php is not an appropriate router for the built in webserver

Currently the built in web server cannot serve static assets with a query string due to the configured router. It serve's HTML instead. Additionally the 'router' will return 200 for non-existent files.

e.g. 
```bash
$ ./app/Console/cake server -p 8080
# In another terminal
$ curl --head http://localhost:8080/img/cake.icon.png
HTTP/1.1 200 OK
Host: localhost:8080
Connection: close
Content-Type: image/png
Content-Length: 943
$ curl --head http://localhost:8080/img/cake.icon.png?
HTTP/1.1 200 OK
Host: localhost:8080
Connection: close
X-Powered-By: PHP/5.4.14
Content-type: text/html
$ curl --head http://localhost:8080/img/NO_FILE
HTTP/1.1 200 OK
Host: localhost:8080
Connection: close
X-Powered-By: PHP/5.4.14
Content-type: text/html
```

Removing the explicitly defined router resolves this. After applying patch, query strings and 404's work:
```bash
$ curl --head http://localhost:8080/img/cake.icon.png?
HTTP/1.1 200 OK
Host: localhost:8080
Connection: close
Content-Type: image/png
Content-Length: 943
$ curl --head http://localhost:8080/img/NO_FILE
HTTP/1.1 404 Not Found
Host: localhost:8080
Connection: close
Content-Type: text/html; charset=UTF-8
Content-Length: 366
```