Merge pull request #557 from muan/muan/hidden

Add !important to [hidden]

Author: jonrohan

modules/primer-base/lib/normalize.scss

@@ -82,7 +82,7 @@ progress {
 
 template, /* 1 */
 [hidden] {
-  display: none;
+  display: none !important;
 }
 
 /* Links