Ensure carousel works in IE10/11

- Drops the `if-supports-3d-transforms()` mixin since all our browsers do support it

- Updates carousel to not rely on that mixin

scss/mixins/_transforms.scss

@@ -1,14 +0,0 @@
-// Applies the given styles only when the browser support CSS3 3D transforms.
-@mixin if-supports-3d-transforms() {
-  @media (-webkit-transform-3d) {
-    // Old Safari, Old Android
-    // http://caniuse.com/#feat=css-featurequeries
-    // https://developer.mozilla.org/en-US/docs/Web/CSS/@media/-webkit-transform-3d
-    @content;
-  }
-
-  @supports (transform: translate3d(0,0,0)) {
-    // The Proper Way: Using a CSS feature query
-    @content;
-  }
-}