Border on checkboxes/radio buttons appears on outside

[anselmbradford]

The border on large contact area selected radio buttons/checkboxes appears on the outside of the button's dimensions, meaning they increase in size by 4 pixels in width and height (seen here). This looks off when there's a group of buttons because the left and right edges do not line up with unselected buttons in the group. I propose the selected state should be kept at the same width/height of the button. I have code for that in cfpb/capital-framework#424