2d3cba06d2
Failed drags bring the element back to where it started; elements are locked to the y-axis, states are represented as CSS classes for styling, elements can be dragged across section/subsection borders, and dragging to the top/bottom of a section Just Works™. Needs some styling love to give visual representation of where the dragged element will drop, though. TODO: It'd be good to have auto expand/collapse for subsections.