v2.5.0

• Feature: Simplify usage by supporting new default loop.
  (#99 by @clue)

  // old (still supported)
  $stdio = new Clue\React\Stdio\Stdio($loop);
  
  // new (using default loop)
  $stdio = new Clue\React\Stdio\Stdio();

• Improve code examples and documentation.
  (#100 by @clue and #98 by @PaulRotmann)

• Use GitHub actions for continuous integration (CI).
  (#97 by @SimonFrings)