Bugfix accounting for Variation Selector 16

[jquast]

Closes #96

• Add new table, VS16_NARROW_TO_WIDE. It has only one version, "9.0.0". This defines a set of characters that are otherwise Narrow, like '0', that become wide when combined with U+FE0F, "VARIATION SELECTOR 16".

• change wcwidth.wcswidth() function, now tracks "last measured character", and, on U+FE0F, checks that character in table VS16_NARROW_TO_WIDE, and, if matching, adds 1 to the measured width.

• add verify-table-integrity.py, this is an unrelated file from previous work in #91 that should have been included there.

• new tests: The latest list of 'emoji-zwj-sequences.txt' and 'emoji-variation-sequences.txt' are fetched by update-tables.py and placed in 'tests/' folder, and now used by automatic tests in test_emoji_zwj.py, this is helpful to ensure 100% compatibility with all latest known emoji sequences

• fix issue with codecov.io token

Note: A single "9.0.0" version is used because of ambiguity in legacy releases of the emoji variation sequences files. So ambiguous, that very few terminals get it right! Details are documented in update-tables.py and I will share results from 'ucs-detect' project shortly.

I believe that U+FE0F is something of a "fixup" for early emojis. I don't expect any new U+FE0F sequences to be published, no changes since release 10.0

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Files	Coverage Δ
wcwidth/table_vs16.py	100.00% <100.00%> (ø)
wcwidth/wcwidth.py	100.00% <100.00%> (ø)

:loudspeaker: Thoughts on this report? Let us know!

[jquast]

This is tested with experimental branch of ucs-detect, sharing draft results shows 100% support for VS-16 as implemented in this branch, for ExtraTermQt, kitty, and zoc, while 91% support in iTerm2 and 88% in cool-retro-term, I think those two are in the area of ambiguity I have documented about.

[jquast]

Testing results published for this branch at URL https://ucs-detect.readthedocs.io/results.html

7 of 25 Terminals have VS-16 support: Konsole, iTerm2, Kovid Goyle's kitty, Terminal.exe, Zoc, ExtratermQt, and cool-retro-term and 2 have partial support, cmd.exe and ConsoleZ