More use of start/end for paddings and margins.

assets/sass/mixins/rtl/_rtl.scss

@@ -4,18 +4,16 @@ $include-rtl: true !default;
 
 // rtl()
 //
-// Includes Right-To-Left language support by adding a parent selector of
-// `[dir="rtl"]`. Since the dir attribute is usually defined on the html element
-// of a page, using this mixin on a ruleset that matches the html element won't
-// work.
+// Includes Right-To-Left language support by adding a selector of
+// `[dir="rtl"]`.
 //
 // Can be turned off globally by setting `$include-rtl: false;`.
 //
-// $selector = '[dir="rtl"]' - The RTL parent selector.
-@mixin rtl($selector: '[dir="rtl"]') {
+// $selector = ':dir(rtl)' - The RTL selector.
+@mixin rtl($selector: ':dir(rtl)') {
   @if $include-rtl {
     @if & {
-      #{$selector} & {
+       &#{$selector} {
         @content;
       }
     }