Incorrect handling of escaping inside code blocks

Input:
<pre>
```
sed 's/\(..\)/\\\x\1/g'
```
</pre>

Debug output:
```
"/home/tdescham/.gem/ruby/2.2.0/bin/wkhtmltopdf"  -q - "/tmp/test.pdf"
<div class="CodeRay">
  <div class="code"><pre>sed 's/\(..\)/\\x/g'</pre></div>
</div>
```
The input code is no longer the same, the triple backslashes became 2, and the \1 backreference disappeared.

Tested with 0.5.9.