renderer: support both QmlWeb v0.1 and v0.2

Author: ChALkeR

renderer.js

@@ -1,7 +1,10 @@
 const remote = require('electron').remote;
 const qmlwebViewer = remote.getGlobal('qmlwebViewer');
 
-const engine = new QMLEngine();
+const Engine = typeof QmlWeb !== 'undefined' && QmlWeb.QMLEngine
+                ? QmlWeb.QMLEngine
+                : QMLEngine;
+const engine = new Engine();
 engine.loadFile(qmlwebViewer.argument);
 engine.start();
 const qml = engine.rootObject;