Use non-blocking send on pid unset, retry on close (#176)

* tinker with async close

* docs

* docs..

* add badfd condition

* lint

* format

* rewrite

* error checking

* fmt

* rewrite

* add else block

* add tests, dumb linter

* linter...

* LINTER

* refactor to use switch

* still tinkering...

* tinkering...

* improve docs

* refactor, again

Prepare v2.6.1 changelog (#171)

Prepare v2.6.0 changelog (#168)

Prepare v2.5.0 release (#150)

Prepare v2.4.0 release (#146)

Prepare v2.3.3 release

Prepare v2.3.2 changelog

Prepare v2.3.1 release

Prepare v2.3.0 changelog

Prepare 2.2.0 release