Fix node 4 support

Author: armano2

lib/rules/no-dupe-keys.js

@@ -16,7 +16,7 @@ function create (context) {
   const usedNames = []
 
   const options = context.options[0] || {}
-  const groups = new Set([...GROUP_NAMES, ...options.groups || []])
+  const groups = new Set(GROUP_NAMES.concat(options.groups || []))
 
   // ----------------------------------------------------------------------
   // Public

lib/rules/no-reservered-keys.js

@@ -15,8 +15,8 @@ const GROUP_NAMES = ['props', 'computed', 'data', 'methods']
 
 function create (context) {
   const options = context.options[0] || {}
+  const groups = new Set(GROUP_NAMES.concat(options.groups || []))
   const reservedKeys = new Set([...RESERVED_KEYS, ...options.reserved || []])
-  const groups = new Set([...GROUP_NAMES, ...options.groups || []])
 
   // ----------------------------------------------------------------------
   // Public