Version 15.4.1

As starting Chrome 55, there is a new event `auxclick` to handle middle click, and `click` doesn't trigger by middle click anymore
https://developers.google.com/web/updates/2016/10/auxclick
/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */
import type {
  TopLevelType,
  DOMTopLevelEventType,
} from 'events/TopLevelEventTypes';
import type {
  DispatchConfig,
  ReactSyntheticEvent,
} from 'events/ReactSyntheticEventType';
import type {Fiber} from 'react-reconciler/src/ReactFiber';
import type {EventTypes, PluginModule} from 'events/PluginModuleType';