Silence the response logger

As mentioned in a [Guacamole issue](https://github.com/triAGENS/guacamole/issues/64) the default Faraday logger is quite chatty. There is absolutely no reason to log the headers all the time. Additionally logging them over multiple lines makes it even harder to read the log file.

This cannot be changed from the outside, thus we need to change in Ashikawa. Logging the headers should still be possible, but with a special flag. Furthermore I would suggest, that we only log the URL in debug mode.