fix build for node 4

Author: Arkadii Berezkin

Diff for: src/rules/no-namespace.js

@@ -31,7 +31,7 @@ module.exports = {
     const firstOption = context.options[0] || {};
     const ignoreFromPatternExpression =
       firstOption.ignoreFromPattern &&
-      new RegExp(firstOption.ignoreFromPattern, 'u');
+      new RegExp(firstOption.ignoreFromPattern);
 
     return {
       'ImportNamespaceSpecifier': function (node) {