adds css front matter escapes

I have a scenario with sass files where if front matter exists in a scss file and I then try to compile it outside of docpad an error "Syntax error: Invalid CSS after "-": expected number or function, was "--cson""

This is caused by sass not being able to recognise the 3 char front matter sequences like ### or ---.
 
I've created a solution that escapes the front matter using css commenting like this:

```css
/*---cson
author: "super ted"
info: "123"
---*/
```

The advantages of this also allows sass\css editors to render the document correctly without reporting errors and discolouring the output.