Lint fixes

[kenorb]

Would you consider the following PR as per #66?

It passes all lint checks.

Fixes #66

[nicolas-grekas]

Which feature of the lib are you using?
Can you use https://github.com/symfony/polyfill-iconv/ instead? (and https://github.com/symfony/polyfill-mbstring/ ?)
If yes, that'd be better: this one is in strict maintenance mode, so I'd prefer not patching it as much as possible.

[kenorb]

It's downloaded via dependency from other Composer projects:

composer $ grep -R "patchwork/utf8" **/composer.json
anahkiasen/underscore-php/composer.json:    "patchwork/utf8": "^1.2"
illuminate/support/Illuminate/Support/composer.json:        "patchwork/utf8": "1.1.*",
patchwork/utf8/composer.json:    "name": "patchwork/utf8",
radic/tmp-underscore-php/composer.json:    "patchwork/utf8": "1.0.*"

[nicolas-grekas]

That's an issue with the linter, not with this lib.