Revert "flexbox for the post header"

This reverts commit bef3084516.

app/assets/stylesheets/common/foundation/mixins.scss

@@ -113,57 +113,3 @@
 	-webkit-transform: $transforms;
           transform: $transforms;
 }
-
-// ---------------------------------------------------
-
-//Flexbox
-
-@mixin flexbox() {
-  display: -webkit-box;
-  display: -moz-box;
-  display: -ms-flexbox;
-  display: -webkit-flex;
-  display: flex;
-}
-
-@mixin inline-flex() {
-  display: -webkit-inline-box;
-  display: -webkit-inline-flex;
-  display: -moz-inline-box;
-  display: -ms-inline-flexbox;
-  display: inline-flex;
-}
-
-
-@mixin align-items($alignment) {
-    -webkit-box-align: $alignment;
-    -webkit-align-items: $alignment;
-    -ms-flex-align: $alignment;
-    -ms-align-items: $alignment;
-    align-items:$alignment;
-}
-
-@mixin order($val) {
-  -webkit-box-ordinal-group: $val;
-  -moz-box-ordinal-group: $val;
-  -ms-flex-order: $val;
-  -webkit-order: $val;
-  order: $val;
-}
-
-@mixin flex($fg: 1, $fs: null, $fb: null) {
-
-	$fg-boxflex: $fg;
-
-	// Box-Flex only supports a flex-grow value
-	@if type-of($fg) == 'list' {
-		$fg-boxflex: nth($fg, 1);
-	}
-
-	-webkit-box-flex: $fg-boxflex;
-	-webkit-flex: $fg $fs $fb;
-	-moz-box-flex: $fg-boxflex;
-	-moz-flex: $fg $fs $fb;
-	-ms-flex: $fg $fs $fb;
-	flex: $fg $fs $fb;
-}