Main margin top in fluid

This prevents fluid layouts from prematurely adding a 50 pixel margin on main to allow for the header spine. I don't understand why this fix is being conflated with August 20th's changes. I branched from master, cleared out any other changes, and isolated the bug. So, the margin top issue in fluid is an exceedingly easy 0.0.1 bug fix if we want to make it before 1.2.0.