Consistent highlighting for special characters (#244)
Consistent highlighting for special characters (#244)

`SpecialChar` currently has no highlighting, but the majority of
other existing `Special` characters in the theme are highlighted as
dark yellow (`htmlSpecialChar`, `texSpecialChar`.)

So, add dark yellow highlighting for `SpecialChar` and change
`perlSpecialString` accordingly, so special characters are highlighted
consistently across all languages.

Resolves #222.

Closes #237.
joshdick/onedark.vim