Merge branch 'merge-conflicts-icon-color' into 'master'

Use warning color merge conflicts icon in MR status widget.

Fixes #18174 

### Before
![Screen_Shot_2016-06-06_at_18.00.56](/uploads/4a74b1710478daee5ee95b7c6b6a835f/Screen_Shot_2016-06-06_at_18.00.56.png)

### After
![Screen_Shot_2016-06-06_at_17.58.04](/uploads/28faefaebef30e4256390029c87b28bb/Screen_Shot_2016-06-06_at_17.58.04.png)

See merge request !4487

app/assets/stylesheets/pages/merge_requests.scss

@@ -108,6 +108,11 @@
       font-size: 17px;
       margin: 5px 0;
       color: $gl-gray-dark;
+
+      &.has-conflicts .fa-exclamation-triangle {
+        color: $gl-warning;
+      }
+
     }
 
     p:last-child {

app/views/projects/merge_requests/widget/open/_conflicts.html.haml

-%h4
+%h4.has-conflicts
   = icon("exclamation-triangle")
   This merge request contains merge conflicts