Fix WOFF files support

**This commit resolves:**
- 'src' and 'local' attributes in 'font-face' CSS values
- invalid font weights and styles

**Upstream bug:**
https://bugs.webkit.org/show_bug.cgi?id=36351 (WOFF files)
https://bugs.webkit.org/show_bug.cgi?id=93853 (Invalid font weights and styles)

**Issues:**
http://code.google.com/p/phantomjs/issues/detail?id=592
http://code.google.com/p/phantomjs/issues/detail?id=247
http://code.google.com/p/phantomjs/issues/detail?id=713