Fixing #221 & #234 where question mark followed by fragment identifier in custom font urls prevents revving.

Custom fonts often have the following "bulletproof" (http://www.fontspring.com/blog/the-new-bulletproof-font-face-syntax) output which doesn't work when rev'ving the font files.

This fixes it by allowing by adding a question mark to the regex.

```css
src:url("/styles/fonts/icons.eot");
src:url("/styles/fonts/icons.eot?#iefix") format("embedded-opentype"),
	url("/styles/fonts/icons.woff") format("woff"),
	url("/styles/fonts/icons.ttf") format("truetype"),
	url("/styles/fonts/icons.svg?#icons") format("svg”);
```