Mutatormath

- Removed ufoLib dependency. Bumped minimum fonttools >= 3.32.0.
- Added ``bend=True`` flag for makeInstance; allows instances to be calculated without the bender transformation.
This is sometimes necessary.

- Assume incoming locations might be plain dicts and wrap them (110).
- Don't fail when reading designspace documents with `format` attribute formatted as a float, as in latest designspace spec (117).

- [ufo.document] Added API to generate a single instance, useful when parallelizing build for fonts with large number of instances.
The DesignSpaceDocumentReader has a new `readInstance` method that reads and builds a single instance element. It takes a `key` tuple argument with the (attribute, value) used to find and select the instance to build (98).

- Write forward slashes as path separators (95).
- Replace Adobe Sans test font with new data with similar range in width and weight, covered by the same license as this package (96).

Updated minimum requirements:
* defcon >= 0.3.5
* fontMath >= 0.4.4

Allow multiple unicode values for glyphs (86).