Merge branch 'improve-white-code-highlight' into 'master'

Improve white code highlight in comments and wiki

![Screenshot 2014-11-05 16.36.55](https://dev.gitlab.org/uploads/dzaporozhets/gitlabhq/5723848593/Screenshot_2014-11-05_16.36.55.png)

See merge request !1241

app/assets/stylesheets/highlight/white.scss

@@ -186,3 +186,11 @@
     }
   }
 }
+
+.readme-holder .wiki, .note-body, .wiki-holder {
+  .white {
+    .highlight, pre, .hljs {
+      background: #F9F9F9;
+    }
+  }
+}