Previously grids would always take precedence when both a grid
and guide were within tolerance of a point.
Now, guides will always take precedence - since they have been
manually set by users we make the assumption that they have
been explicitly placed at highly desirable snapping locations,
and should be selected over the general grid.
Additionally, grid snapping was previously only done if BOTH
x and y could be snapped to the grid. We now snap to the nearest
grid line for x/y separately. This means if a point is close
to a vertical grid line but not a horizontal one it will still
snap to that nearby vertical grid line.
