change for issue #91, #89 and #92, dropped retina support in favor to the WP Retina 2x, add focus support for screenreader only CSS , see: https://github.com/twbs/bootstrap/issues/12199
change for issue #91, #89 and #92, dropped retina support in favor to the WP Retina 2x, add focus support for screenreader only CSS , see: https://github.com/twbs/bootstrap/issues/12199