Fix container not being centered in IE8

Since the header and the footer component use this container it also fixes centering for these components.

src/objects/_width-container.scss

@@ -2,10 +2,6 @@
   // Limit the width of the container to the page width
   max-width: $govuk-page-width;
 
-  @include govuk-if-ie8 {
-    width: $govuk-page-width;
-  }
-
   // On mobile, add half width gutters
   margin: 0 $govuk-gutter-half;
 
@@ -19,6 +15,13 @@
   @include govuk-media-query($and: "(min-width: #{($govuk-page-width + $govuk-gutter * 2)})") {
     margin: 0 auto;
   }
+
+  @include govuk-if-ie8 {
+    width: $govuk-page-width;
+    // Since media queries are not supported in IE8,
+    // we need to duplicate this margin that centers the page.
+    margin: 0 auto;
+  }
 }
 
 @include govuk-exports("govuk/objects/width-container") {