models: add activeBufferChanged signal

When the active buffer is changed on the model, the model
now emits a signal on the rootScope

js/models.js

@@ -4,7 +4,7 @@
  */
 var models = angular.module('weechatModels', []);
 
-models.service('models', ['colors', function(colors) {
+models.service('models', ['$rootScope', 'colors', function($rootScope, colors) {
     /*
      * Buffer class
      */
@@ -160,9 +160,12 @@ models.service('models', ['colors', function(colors) {
                 return buffer;
             }
         });
+
         activeBuffer.notification = false;
         activeBuffer.active = true;
         activeBuffer.unread = '';
+
+        $rootScope.$emit('activeBufferChanged');
     }
 
     /*