A major new feature release, see release announcement.

• Feature: Add event-driven, streaming HTTP client and server implementation via react/http.
  (#440 by @clue)

• Update documentation to link to project meta repo and link to our official Gitter chat room.
  (#432 and #433 by @clue)

• Improve test suite to run tests on PHP 7.4 and add .gitattributes to exclude dev files from exports.
  (#434 by @reedy and #439 by @clue)