Fix: Do not pass $next handler to final request handler. (#308 by @clue)

Fix: Fix awaiting queued handlers when cancelling a queued handler. (#313 by @clue)

Fix: Fix Server to skip SERVER_ADDR params for Unix domain sockets (UDS). (#307 by @clue)

Documentation for PSR-15 middleware and minor documentation improvements. (#314 by @clue and #297, #298 and #310 by @seregazhuk)

Minor code improvements and micro optimizations. (#301 by @seregazhuk and #305 by @kalessil)