message: Closely match primer CSS styles in SubNav
diff: @@ -21,7 +21,7 @@ function SubNavBase({actions, className, align, children, full, label, ...rest})
  const SubNav = styled(SubNavBase)`
  display: flex;
  justify-content: space-between;
  - border-bottom: 1px solid ${get('colors.gray.2')};
  +
  &.SubNav--right {
  justify-content: flex-end;
  @@ -54,20 +54,32 @@ SubNav.Link = styled.a.attrs(props => ({
  activeClassName: typeof props.to === 'string' ? 'selected' : '',
  className: classnames(ITEM_CLASS, props.selected && SELECTED_CLASS, props.className)
  }))`
  - padding: ${get('space.3')}px ${get('space.2')}px;
  - margin-right: ${get('space.3')}px;
  + padding: ${get('space.2')}px ${get('space.3')}px;
  + font-weight: ${get('fontWeights.bold')};
  font-size: ${get('fontSizes.1')}px;
  line-height: ${get('lineHeights.default')};
  color: ${get('colors.gray.6')};
  text-align: center;
  - border-bottom: 2px solid transparent;
  text-decoration: none;
  + border-top: 1px solid ${get('colors.gray.2')};
  + border-bottom: 1px solid ${get('colors.gray.2')};
  + border-right: 1px solid ${get('colors.gray.2')};
  +
  + &:first-child {
  + border-top-left-radius: ${get('space.1')}px;
  + border-bottom-left-radius: ${get('space.1')}px;
  + border-left: 1px solid ${get('colors.gray.2')};
  + }
  +
  + &:last-child {
  + border-top-right-radius: ${get('space.1')}px;
  + border-bottom-right-radius: ${get('space.1')}px;
  + }
  &:hover,
  &:focus {
  - color: ${get('colors.gray.9')};
  text-decoration: none;
  - border-bottom-color: ${get('colors.gray.3')};
  + background-color: ${get('colors.gray.1')};
  transition: 0.2s ease;
  .SubNav-octicon {
  @@ -76,10 +88,9 @@ SubNav.Link = styled.a.attrs(props => ({
  }
  &.selected {
  - font-weight: ${get('fontWeights.bold')};
  - color: ${get('colors.gray.9')};
  - border-bottom-color: ${get('colors.orange.6')};
  -
  + color: ${get('colors.white')};
  + background-color: ${get('colors.blue.5')};
  + border: 0;
  .SubNav-octicon {
  color: ${get('colors.gray.5')};
  }
  