fix(position): fallback for IE8's scrollTop/Left for offset

Author: Romain Laï-King

src/position/position.js

@@ -71,8 +71,8 @@ angular.module('ui.bootstrap.position', [])
         return {
           width: element.prop('offsetWidth'),
           height: element.prop('offsetHeight'),
-          top: boundingClientRect.top + ($window.pageYOffset || $document[0].body.scrollTop),
-          left: boundingClientRect.left + ($window.pageXOffset || $document[0].body.scrollLeft)
+          top: boundingClientRect.top + ($window.pageYOffset || $document[0].body.scrollTop || $document[0].documentElement.scrollTop),
+          left: boundingClientRect.left + ($window.pageXOffset || $document[0].body.scrollLeft  || $document[0].documentElement.scrollLeft)
         };
       }
     };