Give selection change listeners more specific name

src/RichTextEditor.js

     this._onKeyboardWillShow = this._onKeyboardWillShow.bind(this);
     this._onKeyboardWillHide = this._onKeyboardWillHide.bind(this);
     this.state = {
-      listeners: [],
+      selectionChangeListeners: [],
       onChange: [],
       showLinkDialog: false,
       linkInitialUrl: '',
           break;
         case messages.SELECTION_CHANGE: {
           const items = message.data.items;
-          this.state.listeners.map((listener) => {
+          this.state.selectionChangeListeners.map((listener) => {
             listener(items);
           });
           break;
         }
-        case messages.CONTENT_CHANGE: {
-          const content = message.data.content;
-          this.state.onChange.map((listener) => listener(content));
-          break;
-        }
         case messages.SELECTED_TEXT_CHANGED: {
           const selectedText = message.data;
           this._selectedTextChangeListeners.forEach((listener) => {
 
   registerToolbar(listener) {
     this.setState({
-      listeners: [...this.state.listeners, listener]
+      selectionChangeListeners: [...this.state.selectionChangeListeners, listener]
     });
   }