Fix michaelbromley#281 onPageChange callback with oldPageNumber

Author: xldh

src/directives/pagination/dirPagination.js

@@ -309,13 +309,19 @@
 
             function goToPage(num) {
                 if (paginationService.isRegistered(paginationId) && isValidPageNumber(num)) {
+                    var oldPageNumber = scope.pagination.current;
+
                     scope.pages = generatePagesArray(num, paginationService.getCollectionLength(paginationId), paginationService.getItemsPerPage(paginationId), paginationRange);
                     scope.pagination.current = num;
                     updateRangeValues();
 
-                    // if a callback has been set, then call it with the page number as an argument
+                    // if a callback has been set, then call it with the page number as the first argument
+                    // and the previous page number as a second argument
                     if (scope.onPageChange) {
-                        scope.onPageChange({ newPageNumber : num });
+                        scope.onPageChange({
+                            newPageNumber : num,
+                            oldPageNumber : oldPageNumber
+                        });
                     }
                 }
             }