Add support for font related browser hacks.

While trying to use font-awesome via bower, I was stumped by usemin's total lack of substitution of this font on the final minified css file.

This is due to the fonts referenced by awesome-font's stylesheets being:

```css
    @font-face {
      font-family: 'FontAwesome';
      src: url('../font/fontawesome-webfont.eot?v=3.0.1');
      src: url('../font/fontawesome-webfont.eot?#iefix&v=3.0.1') format('embedded-opentype'),
           url('../font/fontawesome-webfont.woff?v=3.0.1') format('woff'),
           url('../font/fontawesome-webfont.ttf?v=3.0.1') format('truetype');
      font-weight: normal;
      font-style: normal;
    }
```

While investigating this I've also bumped on other hacks like this:

```css
    @font-face {
        font-family: 'JinkyRegular';
        src: url(fonts/jinky/JINKY-webfont.eot);
        src: url(fonts/jinky/JINKY-webfont.eot?#iefix) format('embedded-opentype'),
             url(fonts/jinky/JINKY-webfont.woff) format('woff'),
             url(fonts/jinky/JINKY-webfont.ttf) format('truetype'),
             url(fonts/jinky/JINKY-webfont.svg#JinkyRegular) format('svg');
        font-weight: normal;
        font-style: normal;
    }
```

So, this patch adds support for both ```?``` and ```#``` as file name delimiters. It includes tests.

I've already signed the CLA (and have some very very small patches accepted into V8).