Add outlining to grid view
Ensure outline box lines up with baseline grid

God, I am such a fucking nerd.
Adjust horizontal margin to viewport size

On an iPhone, we want the smallest margins possible, but a Mac can have
more room to breathe.
Fix code line-height on iOS
Fix baseline rounding error for h1

On Firefox and Chrome, some sort of rounding bug means a 24px header
won't sit on the baseline. 25px will, so fuck it: use that.