- Don't remove overlaps from empty or all-component glyphs, or else pyclipper fails with an error (27d7b4c, 389).
- Remove pre-existing instance UFOs before calling MutatorMath (6cdf44e, 372).
- Do not round geometry in interpolated instance UFOs. Added a new option `--round-instances` to re-enable old behavior (390).
- Use `font.path` attribute if present to generate the output path (357).
- Support building varfont from designspaces without `<instances>` (5626514).
- Updated minimum installation requirements:
* fonttools >= 3.21.1
* cu2qu >= 1.3.0
* glyphsLib >= 2.2.1
* ufo2ft >= 1.1.0
* MutatorMath >= 2.1.0
* defcon >= 0.3.5
* booleanOperations >= 0.8.0