Trying to remove the scrollbar from the main banner

As pull request since the change works, but I'm not sure it should be committed without a quick discussion.

Seems to be caused by the
```css
overflow: auto;
```
in https://github.com/emanuil-tolev/Co-design/pull/new/master#L0L51

Removing that line entirely moves the 5 B&W logos to the left, on top of the main CO-DESIGN logo. The ```hidden``` value seems to do the trick (idea came from overflow property page here: http://www.w3schools.com/cssref/pr_pos_overflow.asp ).

I'd ask our Designer why it's there - it'd be easier than testing it in various browsers. The question is "why does the browser think there is content that needs a scrollbar" - perhaps a div sizing or just layout issue? So, in essence, why was there a need for an overflow declaration - that should narrow it down.