feat(keyboard): remove listeners from lifecycle events

BREAKING CHANGE: lifecycle listeners will no longer receive field listeners

* Listeners are no longer stored inside Keyboard.
* Field `listeners` was removed from lifecycle events.

Closes #226

lib/features/keyboard/Keyboard.js

@@ -35,7 +35,7 @@ var DEFAULT_PRIORITY = 1000;
  *  - keyboard.init
  *  - keyboard.destroy
  *
- * All events contain the fields (node, listeners).
+ * All events contain one field which is node.
  *
  * A default binding for the keyboard may be specified via the
  * `keyboard.bindTo` configuration option.
@@ -49,16 +49,13 @@ export default function Keyboard(config, eventBus) {
   this._config = config || {};
   this._eventBus = eventBus;
 
-  this._listeners = [];
   this._keyHandler = this._keyHandler.bind(this);
 
   // properly clean dom registrations
   eventBus.on('diagram.destroy', function() {
     self._fire('destroy');
 
     self.unbind();
-
-    self._listeners = [];
   });
 
   eventBus.on('diagram.init', function() {
@@ -131,7 +128,7 @@ Keyboard.prototype.unbind = function() {
 };
 
 Keyboard.prototype._fire = function(event) {
-  this._eventBus.fire('keyboard.' + event, { node: this._node, listeners: this._listeners });
+  this._eventBus.fire('keyboard.' + event, { node: this._node });
 };
 
 /**
@@ -148,7 +145,6 @@ Keyboard.prototype.addListener = function(priority, listener) {
     priority = DEFAULT_PRIORITY;
   }
 
-  this._listeners.push(listener);
   this._eventBus.on(KEYDOWN_EVENT, priority, listener);
 };