Make sure the htmlRelativeFontPath is correct

[SBeator]

The htmlRelativeFontPath should be the relative path from estHtml to o.dest, instead of be the relative path from destHtml to another relative path.

So I just change one line. And this change will fix the bugs:

1. relativeRe generates zero width matches in destHtml
2. If we set destCss or destHtml in task, the src path of the font-face in html will not be correct.

BTW, I am sorry I don't understand your test cases so I didn't add new test for my change.