replaces outdated jQuery.browser call with feature detection

Fixes #69.

Author: usmonster

js/jquery.fn.gantt.js

@@ -185,7 +185,7 @@
             // Normalizes for IE
             elementFromPoint: function (x, y) {
 
-                if ($.browser.msie) {
+                if (!$.support.boxModel) {
                     x -= $(document).scrollLeft();
                     y -= $(document).scrollTop();
                 } else {