Scheduled weekly dependency update for week 16

[pyup-bot]

Update fonttools from 4.7.0 to 4.8.1.

Changelog

4.8.1

---------------------------

- [feaLib] Fixed ``AttributeError: 'NoneType' has no attribute 'getAlternateGlyphs'``
when ``aalt`` feature references a chain contextual substitution lookup
(googlefonts/fontmake648, 1878).

4.8.0

---------------------------

- [feaLib] If Parser is initialized without a ``glyphNames`` parameter, it cannot
distinguish between a glyph name containing an hyphen, or a range of glyph names;
instead of raising an error, it now interprets them as literal glyph names, while
also outputting a logging warning to alert user about the ambiguity (1768, 1870).
- [feaLib] When serializing AST to string, emit spaces around hyphens that denote
ranges. Also, fixed an issue with CID ranges when round-tripping AST->string->AST
(1872).
- [Snippets/otf2ttf] In otf2ttf.py script update LSB in hmtx to match xMin (1873).
- [colorLib] Added experimental support for building ``COLR`` v1 tables as per
the `colr-gradients-spec <https://github.com/googlefonts/colr-gradients-spec/blob/master/colr-gradients-spec.md>`__
draft proposal. **NOTE**: both the API and the XML dump of ``COLR`` v1 are
susceptible to change while the proposal is being discussed and formalized (1822).

Links

• PyPI: https://pypi.org/project/fonttools
• Changelog: https://pyup.io/changelogs/fonttools/
• Repo: http://github.com/fonttools/fonttools

[pyup-bot]

Closing this in favor of #285