Header content spills out of the header on medium-sized screens

[choldgraf]

We are capping the height of our header, which means that if content is too-wide for the screen, it will stack vertically but then spill out of the header. I think instead we'd want the header to expand to contain that content:

The issue is that we're using max-height and height on the header itself. I think instead we want to apply this to the sub-containers within the header, and then make the header just fit its height to its content.