Tighten up `gsub` work
Tighten up `gsub` work

Closes https://github.com/gjtorikian/html-proofer/issues/289

gjtorikian/html-proofer,gjtorikian/html-proofer,gjtorikian/html-proofer,gjtorikian/html-proofer,gjtorikian/html-proofer