shrink event emitting

[Haroenv]

We're currently relying on @algolia/events (a fork of events to ensure the node version isn't taken), but it's a little large (8kb uncompressed) due to its large api surface and it not being builtin. I can see a couple ideas:

• no longer inherit from EventEmitter (breaking change)
• simplify largely what's inside EventEmitter (breaking change, not if it's not inherited)

what could be inside

function EventEmitter() {
  this._events = this._events || {};
}
module.exports = EventEmitter;

EventEmitter.prototype._events = {};

EventEmitter.prototype.emit = function (type) {
  var er, handler, len, args, i, listeners;

  // If there is no 'error' event listener then throw.
  if (type === 'error') {
    if (
      !this._events.error ||
      (this._events.error && !this._events.error.length)
    ) {
      er = arguments[1];
      if (er instanceof Error) {
        throw er; // Unhandled 'error' event
      } else {
        // At least give some kind of context to the user
        var err = new Error(
          'Uncaught, unspecified "error" event. (' + er + ')'
        );
        err.context = er;
        throw err;
      }
    }
  }

  handler = this._events[type];

  if (!handler) return false;

  args = Array.prototype.slice.call(arguments, 1);
  listeners = handler.slice();
  len = listeners.length;
  for (i = 0; i < len; i++) listeners[i].apply(this, args);

  return true;
};

EventEmitter.prototype.addListener = function (type, listener) {
  if (!this._events[type]) this._events[type] = [listener];
  // If we've already got an array, just append.
  else this._events[type].push(listener);

  return this;
};

EventEmitter.prototype.on = EventEmitter.prototype.addListener;

EventEmitter.prototype.removeListener = function (type, listener) {
  this._events[type] = this._events[type].filter(function (l) {
    return l !== listener;
  });

  return this;
};

EventEmitter.prototype.removeAllListeners = function () {
  this._events = {};

  return this;
};

• use the builtin EventTarget (breaking change)
  • node now also supports EventTarget, meaning we wouldn't need a dependency for this anymore? needs to be investigated!