Ufo2ft

- Handle duplicates in glyph postscript names by appending a '.N' suffix to ensure they are unique (or else FontTools fails to decompile font).
Strip invalid characters not allowed by the AGL specification. The only valid characters are:
`[A-Za-z0-9_.]`.
Print a warning if a glyph name exceeds maximum recommended length of 63 characters (274).

None

- Added `overlapsBackend` option to select "pathops" as alternative libary for removing overlaps: https://github.com/fonttools/skia-pathops
- setup.py: added "pathops" to `extras_require`. You can install ufo2ft with support for skia-pathops with e.g. `pip install ufo2ft[pathops]`.
- Added `enum34` to installation requirements, only for python < 3.4. This is a backport of python3's `enum` module.

- Use ``fontTools.misc.fixedTools.otRound`` to round floats to nearest integer towards positive Infinity whenever they have to do with "visual" data like X/Y coordinates, advance widths/heights, and similar (262, 263).

- Bumped minimum required fonttools >= 3.28.
Fixes fonttools/fonttools1275

- Fixed issue when hhea/vhea metrics contain float values which need to be rounded to integers (260).