Change saveString() to saveArrayBuffer()

Change saveString() to saveArrayBuffer() for STL binary exporter.

editor/js/Menubar.File.js

@@ -288,7 +288,7 @@ Menubar.File = function ( editor ) {
 
 		var exporter = new THREE.STLExporter();
 
-		saveString( exporter.parse( editor.scene, { binary: true } ), 'model-binary.stl' );
+		saveArrayBuffer( exporter.parse( editor.scene, { binary: true } ), 'model-binary.stl' );
 
 	} );
 	options.add( option );