Improve style of the warning when mentioning many people in a comment

app/assets/stylesheets/framework/markdown_area.scss

@@ -73,11 +73,9 @@
 }
 
 .referenced-users {
-  padding: 10px 0;
-  color: #999;
-  margin-left: 10px;
-  margin-top: 1px;
-  margin-right: 130px;
+  color: #4c4e54;
+  display: inline-block;
+  padding-top: 10px;
 }
 
 .md-preview-holder {

app/views/projects/_md_preview.html.haml

@@ -15,7 +15,8 @@
       .js-md-preview{class: (preview_class if defined?(preview_class))}
 
   - if defined?(referenced_users) && referenced_users
-    %span.referenced-users.pull-left.hide
+    %div.clearfix
+      %span.referenced-users.hide
         = icon('exclamation-triangle')
         You are about to add
         %strong