It seems this call is duplicated two times. IMO, it would be good to introduce a `BasicToken` which is able to sign request this way. The, we can replace it by:

```
$this->signRequest($request, new BasicToken(base64_encode(
    rawurlencode($this->getConsumer()->getKey()).':'.rawurlencode($this->getConsumer()->getSecret())
)));
```

What do you think?