Add retina logo to Genesis

retina-media-query.css

@media
only screen and (-webkit-min-device-pixel-ratio: 2),
only screen and (   min--moz-device-pixel-ratio: 2),
only screen and (     -o-min-device-pixel-ratio: 2/1),
only screen and (        min-device-pixel-ratio: 2),
only screen and (                min-resolution: 192dpi),
only screen and (                min-resolution: 2dppx) {
    .header-image .site-title > a {
        float: left;
        min-height: 133px;
        width: 100%;
        background: url(images/logo@2x.png) no-repeat left top !important;
        background-size: 175px 133px !important;
    }
  
  @media only screen and (max-width: 850px) {
	.header-image .site-title > a {
 		background-size: 100px 76px!important;
 		min-height: 76px;
		}
	}
}