Background color missing

[transplier]

Somewhat of a dup of #2, but in this case the correct hll class is being generated:

Input (in backticks-ruby):

def test(arg)
  puts arg
end

Output:

<div class="hll"><pre><span></span><span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span>
  <span class="nb">puts</span> <span class="n">arg</span>
<span class="k">end</span>
</pre></div>

This renders with the proper vim colors I specify in markdown-highlighter.ini but the background just isn't there:

Glancing at the stylesheet it looks like the background rule is

.hll .hll { background-color: #222222 }

Not sure why it wants two hll classes.