Adds image-rendering mixin

Author: Corey Csuhta

app/assets/stylesheets/_bourbon.scss

@@ -20,6 +20,7 @@
 @import "css3/box-sizing";
 @import "css3/columns";
 @import "css3/flex-box";
+@import "css3/image-rendering";
 @import "css3/inline-block";
 @import "css3/linear-gradient";
 @import "css3/prefixer";

app/assets/stylesheets/css3/_image-rendering.css

@@ -0,0 +1,17 @@
+@mixin image-rendering ($mode:optimizeQuality) {
+
+  @if ($mode == optimizeQuality) or ($mode == bicubic) or ($mode == bilinear) {
+      image-rendering: optimizeQuality; // Gecko, Presto, Webkit
+      -ms-interpolation-mode: bicubic;
+  }
+
+  @else if ($mode == optimizeSpeed) or ($mode == nearest-neighbor) or ($mode == optimize-contrast) or ($mode == crisp-edges) {
+      image-rendering: optimizeSpeed; // Old versions of Firefox/Gecko, Safari when optimize-contrast not supported
+      image-rendering: -moz-crisp-edges; // Gecko in Firefox 6+
+      image-rendering: -o-crisp-edges;
+      image-rendering: -webkit-optimize-contrast; // Safari/Webkit nightlies
+      -ms-interpolation-mode: nearest-neighbor;
+      image-rendering: optimize-contrast; // As per spec
+  }
+
+}