MarkdownSharp & GitHub syntax for C# code

I have made some light modifications to MarkdownSharp that will transform github flavored fenced code blocks

https://github.com/KyleGobel/MarkdownSharp-GithubCodeBlocks

```cs
Console.WriteLine("Fenced code blocks ftw!");
```

Would become

<pre><code class="language-cs">
Console.WriteLine("Fenced code blocks ftw!");
</code></pre>

It handles the cases I needed to use, there are probably lots of edge cases though, feel free to fork/change/modify/pull request. Markdown sharp has plenty of comments and is all only one file, so it’s not too bad to modify.