Lines longer than 80 characters are edited. Within reason, issues
identified by markdownlint[1] are equally curated.
[1] https://github.com/markdownlint/markdownlint, version 0.12.0
The `gsub` example is incorrect: with pattern `"e+"`, one gets `"m.t m. at th. bar"`. To get `"m..t m. at th. bar"` as documented, the pattern is just `"e"`. Otherwise we could keep "e+" but change the result.
Also removed an extra dot at the end of a sentence.