Add support for more WOFF/WOFF2 flavors (Alternative to #117)

[smasty]

Hi, according to the WOFF File Format 1.0 and WOFF File Format 2.0 specifications,

Although only fonts of type 0x00010000 [...] and 0x4F54544F [...] are widely supported at present, it is not an error in the WOFF file if the flavor field contains a different value, indicating a WOFF-packaged version of a different sfnt flavor. [...] 0x74727565 has been used for some TrueType-flavored fonts on Mac OS.

In the current state, this library only checks for the TrueType flavor (0x00010000), but OpenType flavor (0x4F54544F) fonts are common as well, and those are not correctly identified by this library.

As an alternative to #117, if you're not comfortable with allowing arbitrary flavors, I'm proposing implementing support for the three flavors mentioned in the specification itself: 0x00010000 (already present), 0x4F54544F and 0x74727565.

[h2non]

A new version is available on PyPI. Upgrade it by running: pip install --upgrade filetype