minor fixes for quiet mode

@chrissalij   Did some minor tweaks for removing extra output in quiet mode.

I can't figure out how to remove those "-----------------" at the end, still. I looked all over.

I had to add a dependency to config in Interface, not sure if you like the idea or not. Alternatively, it may be useful to create a "logger" wrapper around puts that can check the config, so you don't need all those "if quiet_mode" all over the place.

Also, this is literally the first time I've ever worked with Ruby, haha. Let me know what you think.