v1.3.0

• Feature: Support request cancellation
  (#75 by @clue)

  $promise = $browser->get($url);
  
  $loop->addTimer(2.0, function () use ($promise) {
      $promise->cancel();
  });

• Feature: Update react/http-client to v0.5,
  support react/stream v0.6 and react/socket-client v0.7 and drop legacy PHP 5.3 support
  (#74 by @clue)