Markdown - RE #23

The problem with this is as @ocha- mentioned, it replaces the contributors on GitHub with the person who renamed the file. I've just tweeted github, with the hope that they may magically fix this issue.

The API call still shows up contributions:
```
curl https://api.github.com/repos/ruby-hacking-guide/ruby-hacking-guide.github.com/contributors
```

Also there's a flag for git to follow the renames, so it must be possible.