Merge pull request #67 from damencho/updates-onDisplayNameChanged

Updates onDisplayNameChanged

JitsiConference.js

     if (!participant) {
         return;
     }
+
+    if (participant._displayName === displayName)
+        return;
+
     participant._displayName = displayName;
     this.eventEmitter.emit(JitsiConferenceEvents.DISPLAY_NAME_CHANGED, id, displayName);
 };