Fix IE8 does not support forEach.

src/extensions/group-by/bootstrap-table-group-by.js

@@ -93,7 +93,7 @@
 
     var groupBy = function (array , f) {
        var groups = {};
-       array.forEach(function(o) {
+       $.each(array, function(i, o) {
            var group = JSON.stringify(f(o));
            groups[group] = groups[group] || [];
            groups[group].push(o);

src/extensions/multiple-sort/bootstrap-table-multiple-sort.js

@@ -328,7 +328,7 @@
         var $multiSortName = this.$sortModal.find('.multi-sort-name').last(),
             $multiSortOrder = this.$sortModal.find('.multi-sort-order').last();
 
-        this.columns.forEach(function(column) {
+        $.each(this.columns, function (i, column) {
             if (column.sortable === false || column.visible === false) {
                 return true;
             }