new features

```shell
./bin/centipede run http://mywebsite --auth-method=session --session-name=SESSNAME --session-id=peigs2pqfjkdr4ms6k3epaamr2 --ignore-url=/app_dev.php/user/logout
```

* Ignore url (one or many)
* Auth user via authenticator, by default we provide SessionAuthenticator, --session-name is PHPSESSID by default. And you can add your own. Auth is totally optional.
* Fix depth, was not given to centipede-crawler before.

PR on centipede crawler is coming.