Problem escaped caracter on IE7. fixes select2#856

Author: ivaynberg

select2.js

@@ -2873,7 +2873,7 @@ the specific language governing permissions and limitations under the Apache Lic
             };
 
             return String(markup).replace(/[&<>"'\/\\]/g, function (match) {
-                    return replace_map[match[0]];
+                    return replace_map[match];
             });
         },
         blurOnChange: false,