Dark theme for code

I have extended the css file for a dark code theme. If the code parts are surrendered by a class "dark", the dark code style will be applied. For exmaple <code class="dark"> class HelloWorld { } </code> or <div class="dark">{% highlight bash %} class HelloWorld { } {% endhighlight %}</div>. If the code is not surrendered by a "dark"-css class, the normal style will be used.