Change so the activity target works

Its probably wrong but the activity target didn't work for me even from you example. Is there any implications in making this change in my code?

js/plax.js

@@ -326,7 +326,7 @@
         if (typeof opts.gyroRange === 'number' && opts.gyroRange > 0) motionDegrees = opts.gyroRange;
       }
 
-      $(document).bind('mousemove.plax', function (e) {
+      plaxActivityTarget.bind('mousemove.plax', function (e) {
         plaxifier(e);
       });