cleaner variable names

examples/specific-element.html

@@ -56,7 +56,7 @@
     <script type="text/javascript">
       $(document).ready(function () {
         $('#shell img').plaxify()
-        $.plax.enable({ "target": $('#shell')})
+        $.plax.enable({ "activityTarget": $('#shell')})
       })
     </script>
 

js/plax.js

@@ -262,6 +262,7 @@
       $(document).bind('mousemove.plax', function (e) {
         if(opts){
           plaxActivityTarget = opts.target || $(window)
+          plaxActivityTarget = opts.activityTarget || $(window)
         }
         plaxifier(e)
       })