Iterating all users fail

```
2019-07-30 15:55:35.319 INFO --- [ main] com.jcabi.http.request.BaseRequest : #fetch(GET myghehost /api/v3/users): [200 OK] in 1s
2019-07-30 15:55:35.568 INFO --- [ main] com.jcabi.http.request.BaseRequest : #fetch(GET myghehost /api/v3/users/1): [404 Not Found] in 200ms
```

Running GHE on-prem 2.17.1

code:
```
Github github = new RtGithub(request);
github.users().iterate("").forEach( user -> {
try {
System.out.println(user.json().toString());
} catch (IOException e) {
e.printStackTrace();
}
});
```

it seems to return the same user on each iteration.

Refdocs: https://developer.github.com/v3/users/#get-all-users