Convert from UFO 2 to UFO 3 source specification

[chrissimpkins]

This should work with all font editors that support UFO source files out there. If you have come across an editor where this is not the case, please weigh in here. Plans are to release the source in UFO 3 format in the upcoming month if there are no objections to this.

[chrissimpkins]

Added in c1c7c62

[chrissimpkins]

This is a massive text diff. Diff of ttf font compiled OpenType tables built from UFO v2 vs. UFO v3 shows no difference & font file checksums are the same vs builds with UFO v2 source when tested at the same commit (with a dirty repo of uncommitted, converted UFO 3 files for the UFO3 compiles).

[chrissimpkins]

Merged to dev. Source spec will be upgraded to UFO v3 from UFO v2 in the master branch as of the tagged v4.000 release.