fix(visibility): jquery scrollleft is a function rather than a property

$context.scrollLeft must be replaced with $context.scrollLeft() otherwise it returns NaN.

Author: lubber-de

src/definitions/behaviors/visibility.js

@@ -902,7 +902,7 @@ $.fn.visibility = function(parameters) {
               element.offset.top += $context.scrollTop() - $context.offset().top;
             }
             if(module.is.horizontallyScrollableContext()) {
-              element.offset.left += $context.scrollLeft - $context.offset().left;
+              element.offset.left += $context.scrollLeft() - $context.offset().left;
             }
             // store
             module.cache.element = element;