Merge branch 'note-username-text-color' into 'master'

Fixed issue with author link color on dark diffs

Correctly added a color to the author link

![Screen_Shot_2016-04-21_at_08.55.05](/uploads/ffa9e12e868c7b71fa4dd9244114274a/Screen_Shot_2016-04-21_at_08.55.05.png)

Fixes #15444

See merge request !3847

app/assets/stylesheets/pages/notes.scss

@@ -183,6 +183,9 @@ ul.notes {
     }
   }
 
+  .author_link {
+    color: $gl-gray;
+  }
 }
 
 .note-headline-light,